Republicans today criticized the president's handling of the milestone, chiding him for taking credit for a moment they say was largely made possible because of policies and strategies implemented by President George W. Bush.
"By adopting the Bush administration's plan for winding down the war and transitioning security responsibilities to the Iraqi military over time, the President has enabled us and the Iraqis to build on the gains our troops have made," said Senate Minority Leader Mitch McConnell.
And several Republicans today pointed out that as a senator Obama had openly opposed Bush's 2007 troop surge strategy, which is now largely seen as having been effective.
"Some leaders who opposed, criticized, and fought tooth-and-nail to stop the surge strategy now proudly claim credit for the results," said House Minority Leader John Boehner. "Today we mark not the defeat those voices anticipated – but progress."
Obama tonight acknowledged the debate over the Iraq war and said he called former President Bush today to discuss the milestone.
"It's well known that [Bush] and I disagreed about the war from its outset. Yet no one could doubt President Bush's support for our troops, or his love of country and commitment to our security," Obama said. "As I have said, there were patriots who supported this war, and patriots who opposed it. And all of us are united in appreciation for our servicemen and women, and our hope for Iraq's future."
The president also used the moment to reiterate his commitment for the strategy in Afghanistan, where thousands of additional U.S. troops have been arriving to battle the Taliban and al Qaeda strongholds.
But he used the model of Iraq to insist that the U.S. will "begin a transition to Afghan responsibility" in July 2011. "Make no mistake," the president said, "this transition will begin - because open-ended war serves neither our interests nor the Afghan people's."
In seeking to "turn the page" on Iraq, Obama also cast attention on what he described as the nation's most pressing challenge: putting millions of Americans back to work at home to "restore our economy."
"This will be difficult," Obama said, "but in the days to come, it must be our central mission as a people, and my central responsibility as President."
Obama's address capped two days of public events marking the milestone. The president met earlier Tuesday with troops and their families at Ft. Bliss in El Paso, Texas. On Monday, he made his second trip to the Army's Walter Reed Medical Center to meet with wounded veterans.
ABC News' Luis Martinez, Kirit Radia and Sunlen Miller contributed to this report.