Debt ceiling financial crunch to come no later than Oct. 17

NEW YORK (CNNMoney) -- Treasury to Congress: The heat's on to raise the country's debt ceiling.

Treasury Secretary Jack Lew said Wednesday he now estimates he will have less cash on hand to pay the country's bills in mid-October than he previously thought.

Instead of the $50 billion he estimated a few weeks ago, he now thinks the cash balance will be closer to $30 billion.

"This amount would be far short of net expenditures on certain days, which can be as high as $60 billion," Lew said in a letter to lawmakers. "If we have insufficient cash on hand, it would be impossible for the United States of America to meet all of its obligations for the first time in our history."

He also said he now estimates the so-called extraordinary measures that the Treasury has been taking since the spring will be exhausted no later than Oct. 17. That's even earlier than originally thought.