At issue is whether to pass a resolution opposing President George W. Bush's decision to send additional troops to Iraq.
The House of Representatives is devoting three days to the debate, which began on February 13.
And the verbal sparring is already impassioned.
The speaker of the House, Nancy Pelosi of the opposition Democratic Party, said the legislature's new leadership is determined to have a voice in Washington's Iraq policy.
"No more blank checks for President Bush on Iraq,” she said. “Our taxpayer dollars must go to protect our troops, to keep our promises to our veterans, and to provide for the safety of the American people,” Pelosi stressed.
Three days of debate will lead to a vote on February 16 on whether to oppose the administration's plan to dispatch additional troops to Iraq.
The lawmakers will vote on a resolution that, in part, states that Congress "disapproves of the decision of President George W. Bush announced on January 10th, 2007, to deploy more than 20,000 additional United States combat troops to Iraq."
Resolution Would Be Nonbinding
The resolution is nonbinding. That means it would have no power to stop the troop deployment, which is currently under way. In that sense, both the debate and vote are symbolic.
But passage of the resolution would still be a setback for Bush, whose Republican Party previously controlled Congress and delivered support for his Iraq initiatives.
The additional troops are the centerpiece of the administration's "surge strategy" to increase security in Baghdad and the Al-Anbar Governorate, the two worst areas of violence in Iraq today.
Supporters of the president are speaking out sharply against the proposed resolution.
The minority leader in the House, John Boehner of the Republican Party, put his opposition this way on February 13. "Do we really believe that if we pack up now and if we abandon Iraq and leave the country in chaos that our enemies are just going to lay down their arms and leave us alone?”
“For too long,” he added, “world leaders responded to terrorism by retreating and just hoping for the best. In a post-9/11 world, this is no longer an option."
First Showdown In Congress Over Iraq
The debate over the resolution is the first major showdown in Congress over Iraq policy since the Democrats won control of both chambers in legislative elections in November.
Last week, Republican lawmakers blocked a vote in the Senate on a similar resolution criticizing the president’s "surge" strategy. Democratic leaders in the Senate have vowed to take up the issue again soon.
Meanwhile, Democrats in the House of Representatives are vowing to put conditions on the president's request for an extra $100 billion to fund the wars in Iraq and Afghanistan.
Among other conditions, they say they will agree to the extra funding only if the administration uses none of the money for permanent bases in Iraq.
That reflects the intention of the Democratic leadership in Congress to place a limit on the number of U.S. troops in Iraq and to press the administration to begin withdrawing soldiers next year.
However, there are deep divisions in Congress over how quickly to pursue troop withdrawals. One reason is concern that a reduction in forces that is done too swiftly could endanger the soldiers that would remain in the country.
The Imam Al-Mahdi Army on parade (epa)
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THE COMPLETE PICTURE: Click on the image to view RFE/RL's complete coverage of events in Iraq and that country's ongoing transition.