Washington ? House Speaker Nancy Pelosi said Thursday that President Bush lacks the authority to invade Iran without specific approval from Congress, a fresh challenge to the commander in chief on the eve of a symbolic vote critical of his troop buildup in Iraq.

Pelosi, D-Calif., noted that Bush consistently said he supports a diplomatic resolution to differences with Iran “and I take him at his word.”

At the same time, she said, “I do believe that Congress should assert itself, though, and make it very clear that there is no previous authority for the president, any president, to go into Iran.”

Pelosi spoke in an interview in the Capitol as lawmakers plowed through a third day of marathon debate in the House on a nonbinding measure opposing the administration’s plan to increase troop strength in Iraq – and as Democrats readied a more provocative challenge to the president.

That included drafting legislation to require the Pentagon to meet certain standards for training and equipping the troops, as well as fixing the time that military units must be given at home between deployments. “That stops the surge (in troops) for all intents and purposes, because … they cannot sustain the deployment,” said Rep. John Murtha of Pennsylvania, who said he would attach the conditions to legislation providing nearly $100 billion for the military.

Republicans quickly fired back. Rep. John Boehner of Ohio, the GOP leader, issued a statement saying the plan would “pull the rug out from under American troops in the combat zone by cutting off their reinforcements and forcing them to face the enemy without our full support.”

Across the Capitol, Senate Majority Leader Harry Reid unexpectedly announced plans to hold a test vote Saturday on the same nonbinding measure critical of the troop increase that was making its way through the House.

Partisan bickering has prevented a Senate vote so far, with Republicans insisting on equal treatment for an alternative that rules out the “elimination or reduction of funds for troops in the field.”

Pelosi and other Democrats have said approval on the nonbinding measure would mark the first step in an effort by the new Democratic-controlled Congress to force Bush to change course in a war that has killed more than 3,100 U.S. troops.

Bush administration officials and their allies are resigned to House passage of the resolution and have worked in recent days to hold down defections by GOP lawmakers.

But Bush, who has challenged lawmakers not to cut off funds for the troops, took a swipe at his critics during the day.

“This may become the first time in the history of the United States Congress that it has voted to send a new commander into battle and then voted to oppose his plan that is necessary to succeed in that battle,” the president said.

The Senate unanimously confirmed Lt. Gen David Petraeus last week to take over as the top U.S. commander in Iraq.