Published 10:25 a.m. ET -- An Obama administration senior official said Tuesday that during the president's State of the Union address he will announce that 34,000 of the 66,000 U.S. troops in Afghanistan will be brought back to the United States within 12 months.

Shamil Zhumatov / Reuters U.S. Army soldiers react after their comrade was wounded at patrol by an improvised explosive device (IED) in southern Afghanistan June 12, 2012.

By this spring, a senior administration official said, Afghan forces will be “assuming the lead across the entire country, with the United States and ISAF (the International Security Assistance Force) stepped back to a train-advise-and-assist role. In that capacity, we will no longer be leading combat operations, but will provide support to the Afghans” during the 2013 and 2014 fighting seasons.

“By the end of 2014, we will responsibly bring our war in Afghanistan to a close,” the official said.

But the Obama administration is in negotiations on a security accord with the Afghan government that would allow some U.S. forces to operate in the country after 2014 to attack remnants of al-Qaida and to train Afghan forces.

Defense Secretary Leon Panetta said in a speech last month “We are still at war in Afghanistan,” but he said the progress the International Security Assistance Force has made in training the Afghan army and Afghan police “has brought us to what I hope will be the last chapter of this war, and the next chapter in NATO's relationship with Afghanistan.”

NBC White House Correspondent Kristen Welker contributed to this story