The Obama administration has insisted that the pledge will stand. But the president's top economic advisers have refused to rule out broad-based tax increases to close the yawning gap between federal revenue and government spending and are warning of tough choices ahead.

Republicans are already on the attack, accusing Obama of plotting to break his no-tax vow, the same political transgression that cost Democrats control of Congress under former president Bill Clinton and may have cost president George H.W. Bush his job.