U.S. Treasury Secretary Timothy F. Geithner

U.S. Treasury Secretary Timothy F. Geithner

Andrew Harrer/Bloomberg

Timothy F. Geithner, U.S. treasury secretary, has warned that a failure to raise the debt ceiling by Aug. 2, the date he now projects borrowing authority would be exhausted, may have catastrophic effects on the U.S. economy by sharply raising borrowing costs.