A resolution criticising President Bush for his decision to send more troops to Iraq is expected to pass the House of Representatives.
Democrats who wrote the non-binding measure say it will set the stage for more decisive steps to constrain Mr Bush's war-waging powers.
They proposed ideas to put legislative strings on future funding in Iraq and prevent any pre-emptive invasion of Iran.
During the first three days of debate, 343 out of the 434 House members - 187 Democrats and 156 Republicans - spoke on the resolution. Democrats supported it, while all but about a dozen Republicans opposed it, warning that it would hurt the morale of the troops and encourage the terrorists.
More than half Americans say the Iraq war is a hopeless cause, according to an poll published today; 38 per cent want to cut money for the additional troops that Mr Bush is sending to Iraq, and 29 per cent want to cut off all funding for the war, the poll found.
"This country needs a dramatic change of course in Iraq, and it is the responsibility of this Congress to consummate that change," said Representative John Murtha, who chairs the House panel that oversees military spending.
He is preparing legislation that would set strict conditions on combat deployments, including a year's rest between combat tours. Ultimately, Mr Murtha says his measure would make it impossible for Mr Bush to maintain his planned deployment of about 160,000 troops for months on end.