THE WHITE HOUSE -- The U.S.-led war in Iraq will end in less than three weeks.

Monday, President Barack Obama and Iraqi Prime Minister Nouri al-Maliki met to discuss "a normalization of the relationship" between the U.S. and Iraq once American troops leave by month's end.

The White House called the prime minister's visit "momentous."

"We're here to mark the end of this war. To honor the sacrifices of all those who made this day possible and to turn the page -- to begin a new chapter of diplomacy," Obama said.

Prime Minister al-Maliki thanked the U.S. for its "commitments," and told reporters that his country is now relying on its own security forces and new security policies.

The United States has invested a tremendous amount of blood, money, and resources in Iraq's future.

By many accounts, Iraq is taking important steps forward. But as President Obama pointed out, the transition won't be easy.

"Our goal is simply to make sure that Iraq succeeds," Obama said.

Some experts fear the Iraqi prime minister will be influenced by his neighbors.

"I think he will easily fall in with Iranian demands that don't fundamentally hurt him directly," said Fred Kagan, with the American Enterprise Institute.

"And that will blow a hole in the strategy for dealing with Iran that the Obama administration is articulating," he said.

Iranian tensions were evident when the leaders were asked about government violence in Syria.

President Obama called on Syrian President Bashar Assad to step down, while Prime Minister al-Maliki warned that civil war would follow Assad's demise and said he can't ask a president to "abdicate his role."

"Even if there are tactical disagreements between Iraq and the United States at this point on how to deal with Syria, I have absolutely no doubt that these decisions are being made based on what Prime Minister Maliki believes is best for Iraq ... not based on considerations of what Iran would like to see," Obama said.

Iraq faces many challenges and al Qaeda is still a threat.

"I would have preferred to see a couple more of them resolved before all of our combat forces were gone," said Michael O'Hanlon of the Brookings Institute. "Not because our combat forces were gonna step in and impose a solution, but because they had a calming effect."

By Dec. 31, the last U.S. troops will leave Iraq, and America will officially establish a more normal relationship with the Iraqi government.