(Updates with details)
WASHINGTON, Feb 12 (Reuters) - President Barack Obama will announce in his State of the Union address on Tuesday that 34,000 troops - about half the U.S. force in Afghanistan - will return by early 2014, a senior administration official said.
Obama and Afghan President Hamid Karzai last month agreed to speed the handover of combat operations in Afghanistan to Afghan forces. There are currently about 66,000 U.S. troops in Afghanistan.
"President Obama will announce that 34,000 U.S. troops will return home from Afghanistan by this time next year, decreasing by half the number of U.S. forces serving in Afghanistan," a senior administration official said.
"Further reductions will continue through the end of 2014 as Afghans take full responsibility for their security," the official said on condition of anonymity.
It will be the latest step toward unwinding the U.S. involvement in the unpopular war in Afghanistan.
Washington's NATO allies have also been steadily reducing their troop numbers despite doubts about the ability of Afghan forces to shoulder full responsibility for security.
Afghan forces were expected to lead military operations across the country by this spring, with U.S. and international forces assisting through training and advising, but no longer leading combat operations, the administration official said.
"By the end of 2014, we will responsibly bring our war in Afghanistan to a close," the official said.
Obama will not make any further announcements about troop numbers in Tuesday's speech, "nor has he made any decisions beyond the one he is announcing," the official said. (Reporting by Tabassum Zakaria; Editing by Jackie Frank and Bill Trott)