Thursday marks the fifth anniversary of the day U.S. President George Bush stood on an aircraft carrier and declared major combat operations in Iraq were over.  Now, some political analysts say the United States is likely to maintain a military presence in Iraq that will last years into the next U.S. presidential administration. Leta Hong Fincher has more.

On 1 May 2003, President George Bush strode onto the deck of the aircraft carrier, USS Abraham Lincoln. Overhead was a banner saying "Mission Accomplished."

President Bush said, "Major combat operations in Iraq have ended.  In the battle of Iraq, the United States and our allies have prevailed."

Five years later, some 140,000 U.S. troops remain in Iraq. More than 4,000 members of the U.S. military have died in the conflict. The number of Iraqi civilians killed in sectarian and other violence is sometimes estimated in the hundreds of thousands.

Anthony Cordesman is a military expert at the Center for Strategic and International Studies in Washington. He says the United States was not prepared for a long-term counterinsurgency, and it will need to maintain a military presence in Iraq for years to come.  "[The war] is winnable," says Cordesman. "It does require patience. I think no one can go to Iraq or Afghanistan without becoming aware that the country teams are talking about a U.S. intervention which will almost certainly last through the life of the next administration."

Cordesman says even after the United States withdraws most of its troops from Iraq, U.S. air support, artillery and ground forces will at times be needed to help the Iraqi military.

With the war dragging on and casualties still mounting, public opinion polls show that a majority of Americans now oppose the war and favor bringing U.S. troops home.

The war has become one of the top issues in the U.S. presidential campaign.

Republican Senator John McCain supports staying the course in Iraq. He told a recent congressional hearing that his goal is for Iraq to no longer need U.S. troops. "But I also believe that the promise of withdrawal of our forces regardless of the consequences would constitute a failure of political and moral leadership," he added.

Democratic Senator Barack Obama pledges to have all U.S. combat brigades out of Iraq within 16 months if elected president. "When John McCain says that the war in Iraq has been a success, when he talks about continuing a war with no exit strategy, a war that has not made us safer, when he talks about maybe keeping troops there for a hundred years, I think the American people understand we can't afford that," said Obama.

Democratic Senator Hillary Clinton says that as president, she would begin to withdraw U.S. troops within 60 days. "We have to restore American leadership and our moral authority, and we will do that by ending the war in Iraq and bringing our troops home as responsibly and quickly as we can," said Clinton.

Political analysts say the growing anti-war sentiment  favors the Democratic Party in the general election.

John Fortier is an expert on U.S. elections at the conservative American Enterprise Institute in Washington.  "People are still - now in higher numbers than ever, in the 60 percent range - saying that the war was not a good idea in the first place, they worry that there is no good outcome to the war," said Fortier. "If you ask a generic question, 'who is better at handling the war, a Republican or a Democrat?' Democrats win that battle.? 

Nonetheless, Fortier says many voters believe McCain has better leadership skills than his Democratic rivals. He adds that U.S. public opinion on the war could easily shift, depending on the level of violence in Iraq.

Analysts say conditions on the ground in Iraq could also limit the decisions a future president makes.