Senate Republicans blocked a no-confidence vote in US Defence Secretary Donald Rumsfeld as Democrats sought to keep attention on the unpopular Iraq war before November's congressional elections.
Trying to stem the drag on their poll numbers caused by Iraq, Republicans denounced as a political stunt the Democrats' resolution urging President Bush to replace Mr Rumsfeld and to "change course in Iraq to provide a strategy for success".
Senator Edward Kennedy, a Massachusetts Democrat, called for "accountability for this breathtaking incompetence which has put our soldiers in daily danger and weakened American national security."
Although Democrats condemned Mr Rumsfeld as a key architect of the war, they said the problem was broader than the secretary and said Mr Bush must abandon failing policies.
Most Democrats want a plan to start withdrawing US troops but without a deadline to complete the pullout; the administration says it will keep troops in Iraq as long as necessary.
With control of both the House of Representatives and the Senate at stake in November's midterm elections, Republicans portrayed Democrats as weak on terrorism, while Democrats decried the administration's handling of the Iraq war in which more than 2,600 US soldiers have died.
Mr Rumsfeld (74) - one of the longest-serving defence secretaries - came under renewed fire last week for a speech to the American Legion in which he likened critics of the administration's Iraq policies to those who appeased Nazi Germany before World War II.
Senator John Kerry, who lost the last presidential election to Mr Bush, called it a "low and ugly political speech, smearing those who dissent from the catastrophic policy."
"I think it's immoral for old men to send young Americans to fight and die in conflict with a strategy that is failing, and a mission that has not weakened terrorism but strengthened it," Mr Kerry said.