Leading US Democrats vowed a push to revise President George W. Bush?s 2002 authorization to wage war in Iraq, as a way to raise pressure for a change in strategy.

Undeterred by Senate Republicans who blocked a resolution opposing Bush?s troop buildup in Iraq, Democrats in control of Congress pledged to challenge Bush anew by seeking a mandate that the mission of US troops does not include interceding in a civil war.

?We?ll be looking at modification of that (war) authorization in order to limit the mission of American troops to a support mission instead of a combat mission,? Senate Armed Services Committee Chairman Carl Levin, a Michigan Democrat told Fox News.With the safety of US troops already in Iraq at stake, Levin said there was little appetite in Congress to cut off funding for the unpopular war, which has raged amid an unrelenting insurgency and sectarian violence. The war already dominates the 2008 White House race. Senate Foreign Relations Committee Chairman Joseph Biden said Congress should ?repeal and restate the president?s authority? to make clear that the US mission in Iraq is ?to protect against al Qaeda gaining chunks of territory, (and) training the Iraqi forces.? Biden, a Delaware Democrat and presidential hopeful, spoke on CBS television?s ?Face the Nation.? Senate Majority Leader Harry Reid, a Nevada Democrat, called the Iraq war ?the worst foreign policy mistake in the history of this country.?