President Barack Obama said Friday that U.S. troops serving in Afghanistan will soon begin shifting from a combat role to one of supporting Afghan security forces.

"Our troops will continue to fight alongside Afghans when needed, but let me say it as plainly as I can: Starting this spring, our troops will have a different mission - training, advising, assisting Afghan forces," he said at a joint press conference with visiting Afghan President Hamid Karzai.

Afghans are increasingly taking the lead in security, allowing the U.S. military to begin the transition to a secondary role, Obama said.

"It will be a historic moment and another step toward full Afghan sovereignty, something I know that President Karzai cares deeply about, as do the Afghan people," he said.

"By the end of next year - 2014 - the transition will be complete," Obama said. "Afghans will have full responsibility for their security, and this war will come to a responsible end."

Regarding the possibility of a continuing U.S. military presence in Afghanistan beyond 2014, he said the only way American forces can remain is if the Afghan government agrees to grant them immunity.

The United States now has some 66,000 military personnel serving in Afghanistan. EFE