Critics of the Bush administration's Iraq policy include Democratic Senator John Kerry, who was his party's presidential candidate in 2004. He blasted the White House for sending more U.S. troops to Iraq, and said he believes there is no military solution to the ongoing violence in the country.

"I get really angry," said John Kerry. "I heard about those four soldiers killed today and I say to myself, as someone who remembers going out on patrols that sort of had a huge question mark over them, what are we doing? What are these kids doing, going out there and finding an IED [improvised explosive device] the hard way?"

The four U.S. troops were killed Sunday by a roadside bomb in Baghdad.

In an effort to quell the violence, the White House in January said it is sending 21,500 additional U.S. troops to Iraq. More recently, the Bush administration announced it is sending 4,700 more troops to Iraq, mostly to serve in a support capacity.

The Bush administration's policy was praised by White House National Security Adviser Stephen Hadley. Speaking on the ABC television program This Week, he acknowledged that some Iraqis want the U.S. military presence to be, in his words, "over."

"But the point is we need to get it in a position where the Iraqis can take responsibility for security successfully," said Stephen Hadley. "Because if we do not and we do a premature withdrawal, then what we have is a situation where, if the Iraqi forces cannot handle the situation, which is the case now, we have Iraq as a safe haven for terrorists, who will destabilize the neighbors and attack us."

U.S. Defense Secretary Robert Gates appeared on the CBS television program Face the Nation to urge critics to wait and see whether the White House's latest troop surge plan is effective.

"General Petraeus, the commander out there, has said it will probably be summer before we know whether we are being successful or not," said Robert Gates. "But I would say that the Iraqis are meeting the commitments they have made to us."

Democratic congressman and prominent critic of the Iraq war, John Murtha, indicated his distrust of the Bush administration's management, in an appearance on CNN's Late Edition.

"Every time they say there is progress, it turns out there is no progress and then they have to backtrack," said Congressman Murtha. "For instance, they say everything is getting better, yet oil production, electricity production are all below pre-war levels. Incidents have increased outside Baghdad."

He said he believes something dramatic needs to be done in order for the situation to get better. He is among supporters of legislation in the House of Representatives that includes a deadline of September 2008 for U.S. troops to be withdrawn from Iraq.

Meanwhile, thousands of people demonstrated in Washington Saturday to show their opposition to the Iraq War. There were others demonstrating in support.

Protests are expected to continue in the United States and elsewhere in the world before Tuesday's four-year anniversary of the start of the war.