President Obama on Tuesday formally announced that U.S. troops have turned over control of Iraq to the country's own government and security forces.

Speaking at the White House, Obama said the U.S. met today's deadline, which is part of the Status of Forces Agreement that was signed under the previous administration. Obama has said since taking office that he plans to follow through on that agreement and remove all troops from Iraq by 2011.

Obama noted that Iraqis are "rightly treating this day as a cause for celebration," but he also noted that challenges still lie ahead.

"With this progress comes responsibility," he said. "Iraq's future is in the hands of its own people."

He also said he expects there to be "difficult days" in the future and said he expects continued violence in the country. A deadly car bomb in Kirkuk on Tuesday is just one example that the country is not entirely secure, the president said.

Obama also thanked U.S. soldiers for their work in the country.

"Our troops have overcome every obstacle to extend this opportunity to the Iraqi people," Obama said.

This post was updated at 3:15 P.M.