President Obama is planning to remove half of the 68,000 U.S. troops in Afghanistan by the end of the year, setting the stage for the eventual withdrawal of all American service members by 2014.
Obama is expected to provide details about moving 34,000 American soldiers, sailors, airmen and Marines from Afghanistan during Tuesday's State of the Union address, The Hill has confirmed.
The planned drawdown falls in line with the postwar recommendations of former U.S. commander in Afghanistan Gen. John Allen as well as others inside the Pentagon, a senior White House official said.
"The president made his decision based on the recommendations of the military and his national security team, as well as consultations with [Afghan president Hamid] Karzai and our international coalition partners," the official said.
On Tuesday, Senate Armed Services Committee ranking member John McCainJohn McCainThe Obama presidency that never was Week ahead: Comey under fire; Lawmakers look for Russia response McCain leans toward voting for Tillerson MORE (R-Ariz.) refused to make a "snap judgment" on whether the White House's withdrawal proposal would harm future U.S. efforts in the country.
"I have always been concerned about too few troops [in Afghanistan] and withdrawing more quickly, but I can't make a snap judgment without looking at the whole proposal," McCain said, noting the details of the plan are not yet official.
Obama personally informed Karzai, British Prime Minister David Cameron and German Chancellor Angela Merkel of his plans to announce the troop withdrawal on Tuesday, the official added.
The scheduled troop withdrawal falls in line with the administration's decision earlier this year to hand over control of all security operations to Afghan National Security Forces ahead of schedule.
That transition had been scheduled to take place sometime in early 2014 but will now take place this spring.
The decision was made after one-on-one talks between Obama and Karzai during the Afghan leader's trip to Washington in January.
While the U.S. will still have more than 30,000 troops in Afghanistan after this year, those forces will take a backseat to Afghan commanders who will have the lead in battling the Taliban and other Islamic extremist groups operating in the country.
“In that capacity, we will no longer be leading combat operations but will provide support to the Afghans as they lead [combat] operations," the White House official said. "By the end of 2014, we will responsibly bring our war in Afghanistan to a close."
One sign of the accelerating U.S. withdrawal from Afghanistan came Monday, when the first tranche of U.S. weapons and equipment began filtering across the Afghanistan-Pakistan border.
— Amie Parnes contributed to this report.
--This report was updated at 3:34 p.m.