President Obama and Afghan President Hamid Karzai on Friday announced a quicker transition of control of Afghanistan to the nation's own security forces, saying U.S. troops would move to a support role this spring.

In a joint press conference at the White House, Obama said the transition would lay the foundation for a drawdown of U.S. troops but did not say how quickly that would occur — or if any American forces would remain in Afghanistan after 2014.

“Starting this spring our troops will have a different mission: training, advising and assisting Afghan forces,” Obama said. “It will be a historic moment.”

Obama’s comments came after the two leaders discussed troop levels, security and the 2014 Afghan election, among other issues.

The war in Afghanistan has come at great cost in both treasure and casualties for the United States. As such, the president was hesitant to label the war a complete success.

“We have achieved our central goal or have come close to achieving our central goal,” he said.

But then he added, “Have we achieved everything that some might have imagined us achieving under the best of scenarios — probably not.”

Karzai welcomed the accelerated transition, saying that by the spring, no foreign troops would occupy Afghan villages.

For Obama, the main question remains how many troops will stay in Afghanistan after December 2014. The White House earlier this week conceded that it was weighing whether to remove all U.S. troops.

On Friday, the president said he would wait for recommendations from his military leaders before making a decision.

U.S. commanders have recommended keeping as many as 15,000 troops in Afghanistan in a support role, but the administration has shown little appetite for that type of presence after 2014.

Obama had previously said the U.S. cannot leave troops in Afghanistan unless they receive immunity from prosecution.

Karzai announced on Friday that he could now “go to the Afghan people” and press for immunity for American troops in the country.