WASHINGTON (CNN) -- One of the leading House Democrats on defense issues on Thursday called for a swift U.S. withdrawal from Iraq, drawing strong criticism from Republicans and escalating the debate over President Bush's war policies."U.S. and coalition troops have done all they can in Iraq," said Rep. John Murtha, a Pennsylvania Democrat who has been in Congress for 31 years. "It's time for a change in direction."Murtha warned that other global threats "cannot be ignored."Murtha, a retired Marine colonel who earned a Bronze Star and two Purple Hearts for his service in Vietnam, said he believes all the forces could be redeployed over a six-month period. (Watch Murtha's take on 'flawed policy wrapped in illusion' -- 8:11)Understanding that Murtha is considered hawkish on defense issues and is influential with both parties, administration officials said they take solace that moderate Democrats have not raced to join Murtha's call.The White House initially said Bush "respectfully disagrees" with Murtha.But a statement issued Thursday night by Bush spokesman Scott McClellan compared Murtha with anti-war filmmaker Michael Moore and echoed earlier statements by House GOP leaders in accusing him of "surrender."And Speaker Dennis Hastert, an Illinois Republican, blasted Murtha for his comments."It is clear that [House Minority Leader] Nancy Pelosi's top lieutenant on armed services, Rep. Murtha, and Democratic leaders have adopted a policy of cut-and-run," Hastert said in a statement. "They would prefer that the United States surrender to the terrorists who would harm innocent Americans."Rep. Duncan Hunter, a Republican from California and chairman of the House Armed Services Committee, described calls for withdrawing U.S. troops from Iraq "a mistake," arguing that leaving Iraq would make it appear that the United States cannot sustain prolonged military operations.A respected voice"Now is the time for endurance," Hunter said. "We're changing a very strategic part of the world in such a way that it will not be a threat to the United States and, in fact, will be an ally in the global war against terror."Murtha's call could have a significant impact on the debate over the future of the Iraq war, because both Democrats and Republicans seek his advice on military and veterans issues.So far, about two dozen Democrats and just three Republicans in the House have put their names to measures demanding a withdrawal from Iraq. Only one senator, Wisconsin Democrat Russ Feingold, has openly advocated a U.S. pullout, though others have urged President Bush to develop a timetable for an eventual U.S. withdrawal. "A man of the stature of John Murtha -- that's a pretty heavy hit, I don't mind telling you," said North Carolina Republican Rep. Walter Jones, sponsor of the House resolution that calls for a timetable for withdrawal. "He ... gives a lot of weight to this debate." Jones said this will make "some Republicans think about their responsibility as relates to the war in Iraq" and that "this is a week that will help further the debate -- ignite the debate."Another Democrat who voted for the war, Rep. Harold Ford of Tennessee, said he had heard of Murtha's comments and wouldn't endorse his call for immediate withdrawal.But, Ford said, "It's a powerful statement coming from arguably the most respected voice in the Congress," and it will be hard for the White House and Vice President Dick Cheney to dismiss these comments as easily as other Democratic criticisms on the war.Presence 'uniting enemy against us'Murtha is the senior Democrat and former chairman on the Defense Appropriations Committee and voted in favor of the Iraq war. Now, he said, the presence of U.S. troops in Iraq is "uniting the enemy against us." (Watch Jeff Greenfield's comparison of Iraq and Vietnam -- 4:07)"Our military has accomplished its mission and done its duty," he said. "Our military captured Saddam Hussein, captured or killed his closest associates, but the war continues to intensify."He said the redeployment will give Iraqis the incentive to take control of their country.The statement comes amid increasingly heated debate over the Iraq war and the intelligence leading up to the March 2003 invasion. A recent CNN/USA Today/Gallup poll also found the public increasingly dissatisfied with the Iraq war. The poll, released Monday, found that 60 percent of Americans said the war was not worth fighting, while 38 percent said it was worthwhile. (Full story) Monday's poll found that 19 percent of Americans want to see the troops come home now and 33 percent said they wanted them home within a year. Only 38 percent said they should remain "as long as needed." On Tuesday, the Senate also voted 79-19 for an amendment "to clarify and recommend changes" to U.S. policy in Iraq. The vote was seen as a reflection of the increasing bipartisan dissatisfaction over the war's progress.On Wednesday, Vice President Dick Cheney dismissed Democratic critics, calling allegations that the administration misled the country as "dishonest and reprehensible charges." (Full story)'Flawed policy'Murtha took issue with the administration's counter-criticism."I like guys who've never been there who criticize us who've been there," Murtha said. "I like guys who got five deferments and never been there and sent people to war and then don't like to hear suggestions that what may need to be done." Cheney avoided military service in the 1960s with a series of draft deferments, and Bush served stateside in the National Guard during Vietnam."I resent the fact that on Veterans Day, they criticized Democrats for criticizing them," Murtha said, referring to a speech Bush gave in Pennsylvania. (Full story)"This [the war] is a flawed policy wrapped in illusion. The American public knows it, and lashing out at critics doesn't help a bit," Murtha said. "You've got to change the policy. That's what's going to help the American people."Murtha -- who recently visited Iraq's Anbar province -- said it is Congress' responsibility to speak out for the "sons and daughters" on the battlefield, and he relayed several emotional stories from soldiers recovering at Walter Reed Medical Center in Bethesda, Maryland."I tell you, these young folks are under intense activity over there, I mean much more intense than Vietnam," he said. "You never know when it's going to happen."CNN's Dana Bash and Deirdre Walsh contributed to this report.