VETO THREAT: A White House threat to veto legislation that would avert a debt default pushed stocks lower Tuesday.

THE IMPASSE: The stalemate over raising the country's borrowing limit has rattled investors. If an agreement is not reached by Aug. 2, the U.S. won't have enough cash to pay all its bills and could default on its debt.

INDEXES: The Dow Jones industrial average fell 91.50 points, or 0.7 percent, to 12,501.30. The Standard & Poor's 500 index fell 5.49 points, or 0.4 percent, to 1,331.94. The Nasdaq composite fell 2.84, or 0.1 percent, to 2,839.96.