Treasury Secretary Geithner tells Congress that the U.S. will reach its legal debt limit by May 16 and urges lawmakers to act soon.

The Treasury Department’s arsenal of emergency measures may provide extra borrowing room to last only until about July 8, Treasury Secretary Timothy F. Geithner said today.

“The longer Congress fails to act, the more we risk that investors here and around the world will lose confidence in our ability to meet our commitments and our obligations,” Geithner said in a letter to Senate Majority Leader Harry Reid and other members of Congress. “Default by the United States is unthinkable.”