(CNN) -- The top U.S. commander in the Pacific called repeated North Korean violations of U.N. Security Council resolutions forbidding the "building and testing" of long-range ballistic missiles and nuclear weapons "a clear and direct threat to U.S. national security and regional peace and stability."
"A major conflict in Korea could have unpredictable, long term, and far reaching impacts due to the central location of the Korean peninsula in Northeast Asia and the vital importance of Northeast Asian trade to the global economy," said Adm. Samuel J. Locklear, commander of the U.S. Pacific Command.
The admiral spoke at a Senate Armed Services hearing Tuesday and submitted testimony to the committee.
He said he's confident that the United States would be able to help defend U.S. forces and its friends. Asked if the United States is prepared for a fight, if that day ever comes, Locklear said, "We're ready." He also acknowledged the importance of China's role in reducing tensions on the Korean Peninsula.
The hearing came as North Korea issued its latest dispatch of ominous rhetoric Tuesday, telling foreigners in South Korea they should take steps to protect themselves in the event of a conflict on the Korean Peninsula.
North Korea's latest warning of possible war was "more unhelpful rhetoric that serves only to escalate tension," White House spokesman Jay Carney said Tuesday, repeating the Obama administration's assertion that a diplomatic solution exists.
"Kim Jong Un's stated emphasis on economic development and promises of economic growth have so far yielded little, and are undermined by North Korean missile launches and nuclear tests that lead to further sanctions and international isolation," Locklear said, referring to North Korea's leader.
Locklear said the United States had at first been "cautiously encouraged in February 2012" when Pyongyang "agreed to implement a moratorium on "long-range missile launches, nuclear tests and nuclear activities at Yongbyon."
"However, Pyongyang almost immediately broke its promise by attempting to place a satellite into orbit using proscribed ballistic missile technology and parading an alleged road mobile intercontinental range ballistic missile system," Locklear said.
"Pyongyang responded to the unanimous U.N. condemnation of its December launch with renewed rhetoric, threats and bluster. Just a few weeks ago, again in clear violation of U.N. resolutions, North Korea announced it had conducted its third nuclear test, which it claimed -- without any evidence -- was a smaller, more powerful weapon." he said.
"North Korea's nuclear weapons and ballistic missile programs, its illicit sales of conventional arms, and its ongoing proliferation activities remain a threat to regional stability and underscore the requirement for effective missile defense," he said.
Tensions and fears
The admiral was asked by Sen. John McCain, R-Arizona, if there's ever been a time of greater tension among North Korea, South Korea and the United States since the end of the Korean War in the 1950s.
"I would agree in my recollection, I don't know a greater time," he said.
He was asked about how the United States would be able to respond to launches. He said he would recommend intercepting a North Korean missile only if it were in defense of the United States and its allies.
Would you recommend that we intercept a missile, McCain asked, "if it is launched by North Korea, no matter where the intended target is?" In that case, Locklear said, he wouldn't make that particular call.
However, he said, the "architectures that we have of, you know, we will be able to sense and be able to understand pretty quickly where any launch from anywhere in the world, but in this case from this particular site, where it would probably -- where it would be going -- and what we need to do about it," he said.
"So I'm confident that we would be able to make that decision for defense of our allies and our homeland."
The question of China
Asked about China and its longtime close relationship with North Korea, he said the country could play a key role in persuading the North Korean government to engage in "restraint," but "they could do more."
Senators expressed concerns, skepticism and outright criticism of China. Sen. Lindsey Graham, R-South Carolina, called the country "a communist dictatorship" that fears individual freedoms.
Locklear regards China as neither a friend nor a foe.
He said that sometimes, China can be "more nuanced" than the United States, and he noted some reporting that the leadership in China has made some statements about the issue.
The other day, Chinese President Xi Jinping was quoted as saying that no nation "should be allowed to throw a region and even the whole world into chaos for selfish gain. While he didn't mention North Korea, the comments were seen as a reference to Pyongyang.
China, an emerging economic powerhouse, and the United States share a similar interest: peace and security, Locklear said.
In time, he said, China will calculate that North Korea's actions are not in China's national interests. They'd be concerned about weapons of mass destruction, border security and refugee flow if any military conflict should arise.
"There no benefit to the Chinese of having this type of activity occurring on their borders, no possible benefit that I can see from this. So they will, I believe, in time, work this problem to their national interest just like we do and the South Koreans do," he said "My sense is that they will look after their national interests."
The forced budget cuts are considered worrisome
Throughout Locklear's testimony, he noted the dangers but stressed the importance of responding to the problem properly and not miscalculating.
Locklear also expressed concern about how the forced budget cuts in the United States known as sequestration will affect operational readiness in the future.
The command has managed assets inside its area of operations for now, he said, noting that "it has not limited my ability to date." He said he's concerned about the future.
He was asked if he'd be able to carry out "security requirements to defend this nation if sequestration continues the path that it's on."
"It depends on how the resources globally are prioritized and if they're prioritized to the Pacific," he said.
Gen. James D. Thuman, the commander of the U.N. Command, Combined Forces Command, U.S. Forces Korea, was to testify at the hearing, which is devoted to the U.S. military posture throughout Asia. But it was decided to keep him on the Korean Peninsula because of the crisis there.
The saber rattling is making an impact, poll says
Meanwhile, the storm of warlike words coming from Pyongyang appears to have rattled Americans, with more than four in 10 saying they see the reclusive nation as an immediate threat to the United States, a new CNN/ORC International poll shows.
That's up 13 percentage points in less than a month, CNN Polling Director Keating Holland said.
"If North Korean leader Kim Jong Un wanted to get the attention of the American public, his strategy is starting to work," Holland said.
North Korea's unnerving message advising foreigners to secure shelter or evacuate in case of hostilities came as Japan set up missile defenses in Tokyo, and North Korean workers failed to turn up for work in the industrial complex jointly operated by North and South Korea.
In the statement published by state-run media Tuesday, the North's Korea Asia-Pacific Peace Committee reiterated accusations that Washington and Seoul are seeking to provoke a war with Pyongyang.
"Once a war is ignited on the peninsula, it will be an all-out war," the committee said, adding that North Korea doesn't want foreigners in South Korea to "fall victim" to a conflict.
It follows a warning from the North last week to diplomats in its capital city, Pyongyang, that if war were to break out, it would not be able to guarantee their safety.
But staff at the British Embassy in Seoul appeared unimpressed by the North's most recent attempt to rattle nerves in the region.
"We are not commenting on the specifics of every piece of rhetoric from North Korea," said Colin Gray, head of media affairs at the embassy. "Our travel advice remains unchanged. At this moment, we see no immediate threat to British citizens in South Korea."
Several Western countries said last week they had no plans to withdraw staff from Pyongyang after the North's warning to diplomats there.
And foreign visitors in Seoul didn't appear to be panicking Tuesday.
"I am concerned, but not enough not to make the trip," said Vicky Polashock, who was visiting from Atlanta.
She said that there was more tension than she'd noticed on previous visits to South Korea, but that the North's latest threat "doesn't heighten the danger any more than the last couple of weeks."
Threat after threat
North Korea has unleashed a torrent of dramatic threats against the United States and South Korea in recent weeks, including that of a possible nuclear strike. But many analysts have cautioned that much of what Kim's regime is saying is bluster, noting that it is believed to still be years away from developing an operational nuclear missile.
A more likely scenario, they say, is a localized provocative move.
Amid the fiery words from Pyongyang and annual military training exercises by U.S. and South Korean forces in the region, government officials in Washington and Seoul say they are taking the North Korean threat seriously.
The North was blamed for two attacks on South Korea in 2010, one on a navy vessel and another on the island of Yeonpyeong. Those attacks killed 50 people. Pyongyang still denies responsibility for the sinking of the South Korean warship, the Cheonan, in which 46 sailors died.
On Tuesday, Japan said it had deployed missile defense systems around Tokyo amid expectations that the North could carry out a missile test in the coming days.
The Japanese government is making "every possible effort to protect the Japanese people and ensure their safety," said Prime Minister Shinzo Abe.
The Patriot missile batteries were set up in the central Tokyo district of Ichigaya and in the suburbs of Asaka and Narashino, authorities said.
South Korean government officials have said they think North Korea could conduct the test launch of a missile as soon as Wednesday, following reports that the North had loaded as many as two medium-range missiles onto mobile launchers on its east coast.
The United States had previously said it was moving missile defense systems to Guam, a Western Pacific territory that is home to U.S. naval and air bases. North Korea has cited those bases when listing possible targets for missile attacks.
A symbol of cooperation at risk
The souring situation on the Korean Peninsula was in evidence in the failure of more than 50,000 North Korean workers to show up for work Tuesday morning at the Kaesong Industrial Complex, the manufacturing zone shared by the two Koreas that had operated without such an interruption for eight years.
The North had declared Monday that it would pull out its workers and temporarily suspend activities at the complex, which sits on its side of the heavily fortified border but houses the operations of more than 120 South Korean companies.
On Tuesday, the South Korean Unification Ministry said the North Korean workers hadn't reported for work in the district, which is the last major symbol of cooperation between the two Koreas.
Analysts had expressed skepticism that Pyongyang would follow through on previous threats to shut down the complex, noting that it is an important source of hard currency to Kim's regime.
The move also is likely to put pressure on the city of Kaesong itself, where the North Korean workers and their families live. With an estimated population of between 200,000 and 300,000 people, it is one of the impoverished country's largest cities.
South Korean officials criticized the North's decision to halt activities at Kaesong, with President Park Geun-hye saying Tuesday that it risked damaging its credibility as a place to do business.
Since last week, the North had been blocking South Koreans from entering the zone, depriving the factories of key personnel and supplies. The entry ban had already prompted more than 10 of the companies to cease production.
As of Tuesday, 406 South Koreans and two Chinese remained inside the industrial complex, the South Korean government said.
The North had blocked South Koreans from going into the complex before, in March 2009. But it returned the situation to normal in a matter of days and didn't withdraw its own workers from the factories.
Anger about sanctions
North Korea stepped up its efforts to stir tensions in the region after the U.N. Security Council imposed stricter sanctions for Pyongyang's latest underground nuclear test, which took place in February.
Shows of strength by the U.S. military during the current training exercises with South Korea have provided extra material for the North's verbal broadsides.
The United States has since dialed back its military displays to avoid any further escalation of the crisis. It postponed a missile test scheduled for this week in California to prevent any misreading of the situation by Pyongyang.
But North Korea is sticking to its claim that it needs its own nuclear weapons as a deterrent to the threat it perceives from the United States. And it is demanding to be recognized globally as a nuclear power.
Last week, Pyongyang said it would restart a nuclear reactor that it had shut down five years ago under an agreement with Washington, Seoul, Beijing and other parties.
It has also severed a key military hotline with the South, and said it was ditching the armistice agreement that stopped the Korean War in 1954. Because that war ended in a truce and not a formal peace treaty, the two Koreas technically remain at war.