Geithner said he would have to suspend investments in federal retirement funds until August 2 in order to create room for the government to continue borrowing in the debt markets.

The funds will be made whole once the debt limit is increased, Geithner said. "Federal retirees and employees will be unaffected by these actions."

He went on to urge Congress once again to raise the country's legal borrowing limit soon "to protect the full faith and credit of the US and avoid catastrophic economic consequences for citizens."

Congress, meanwhile, is not showing any signs of budging. Many Republicans and some Democrats say they won't raise it unless Congress and President Obama agree to significant spending cuts and other ways to curb debt.

Geithner told Congress that he estimates he has enough legal hoop-jumping tricks to cover them for another 11 weeks or so.

But then he said that's it. If lawmakers don't get it together by August 2, the US will no longer be able to pay its bills in full.