Critic: Sen. Jim Webb (D). lawrence jackson/ap/file

Washington - One of the US Senate's harshest critics of the Iraq war, Jim Webb (D) of Virginia, is warning that the strategic agreement the Bush administration is negotiating with the Iraqi government will hamstring the next president's ability to change course on the war.

Senator Webb acknowledged the lack of Senate support for mandating that President Bush change course. The Virginia senator, whose squeaker 2006 election from a red state symbolized the electorate's disapproval of the war, says anything Congress can do about the war "is really around the edges."

Webb's discussion of the Iraq war with reporters at a Monitor breakfast Wednesday was one of many events in Washington marking the war's fifth anniversary. Mr. Bush spoke at the Pentagon to civilian and military employees about what he called the successes of a war he ordered to begin this day five years ago.

At the same time, antiwar protesters rallied outside government buildings and marched in black clothing and skull masks – to represent the nearly 4,000 US soldiers who have died in the conflict.

Webb highlighted the negotiations under way between the United States and the government of Iraqi Prime Minister Nouri al-Maliki.

"The new president is going to inherit this agreement," he said, adding that any agreement the Bush administration reaches will make it "more difficult for a Democratic president to change course than for a Republican to continue the same course."

By August, the administration hopes to conclude agreements with Iraq that will define how, where, and in what capacity US forces will remain in the country. One is a status of forces agreement. The potentially more far-reaching is a strategic framework agreement that could cement US-Iraq relations for years to come.

Administration officials insist any agreement will not tie the hands of a future president, but critics like Webb counter that any agreement with a foreign government would be difficult to undo.

Moreover, Webb says such an agreement is really a treaty and requires Senate confirmation, while the administration plays down documents as lower-level agreements that don't require congressional approval.

The Webb breakfast and Bush's Pentagon speech provided a point-counterpoint on the Iraq war in terms of one of its original objectives in the aftermath of the 9/11 attacks: to further the international war on terrorism.

Bush pointed to last year's Sunni uprising in Iraq's Anbar Province against Al Qaeda forces. He also noted that the year-old "surge" of 30,000 US troops in Iraq allowed the US to develop a closer relationship with Sunnis who had been living under the yoke of Al Qaeda in Iraq. "The surge has done more than turn the situation in Iraq around – it has opened the door to a major strategic victory in the broader war on terror."

Bush said, "In Iraq, we are witnessing the first large-scale Arab uprising against Osama bin Laden, his grim ideology, and his terror network."

Countering that view, Webb ticked off a list of familiar criticisms that the war helped Al Qaeda enter Iraq, and that the US focus there has allowed Al Qaeda and other forces of extremism to flourish elsewhere. "Al Qaeda is fluid mobile – you see their resurgence in Afghanistan [and] we can't separate that from Iraq."

As for Bush's picture of Sunni Arabs joining the US to drive out Islamist extremists, Webb countered with what he says his son – a Marine deployed to the Anbar city of Ramadi – told him about the province's change of heart. "He said the former insurgents going after Al Qaeda is truly redneck justice." It's an example of the local population becoming fed up with the outsiders who ended up oppressing them, and acting on it.

Himself a former marine, Webb said he does "not want to be in a position of down playing what the military is doing" in Iraq. But he advocates stepped up diplomatic intervention with Iraq's neighbors as a prelude to reducing the US footprint in Iraq.

In response to a question about his political future, Webb said he is "not particularly" interested in the vice-presidential slot on the Democratic ticket. When one reporter quipped that this was "a pretty weak no," Webb added that "not particularly … is not almost a yes."