President Barack Obama is expected to announce this week that 30,000 U.S. "surge" forces will be fully withdrawn from Afghanistan by the end of 2012, an administration official has told CNN.
Obama will deliver his highly anticipated speech on the troop drawdown on Wednesday.
The time-frame would give U.S. commanders another two "fighting" seasons with the bulk of U.S. forces still available for combat operations. Outgoing Defense Secretary Robert Gates has pushed for additional time to roll back Taliban gains in the country before starting any significant withdrawal - a position at odds with a majority of Americans, according to recent public opinion surveys.
Gates acknowledged Tuesday that domestic public opinion and congressional support for further military engagement must be taken into account by the president.
"Sustainability here at home" is an important consideration, Gates said. People are "tired of a decade of war."
An estimated 100,000 U.S. troops are currently serving in Afghanistan, some 30,000 of which are part of the so-called surge ordered in late 2009 in a bid to control the rising violence.
Obama has been mulling how many troops should be withdrawn this summer and by the end of the year.
The president is expected, in his remarks Wednesday, to stress the importance of preserving flexibility in force levels on the ground so commanders can adjust as conditions warrant, the official said.
The drawdown will be accomplished by troops returning home and not being replaced as well as cancelling some proposed deployments.
On Monday, White House Press Secretary Jay Carney told reporters that Obama had yet to make a final decision on the size and scope of the troop withdrawal, but would do so "soon."
"The president is still in a process of finalizing his decision on the pace and scope of the drawdown that will begin in July of 2011," Carney said . "He's finalizing his decision. He's reviewing the options and the assessments and will have an announcement to make soon."
Obama has said troops would begin coming home in July, and he recently indicated the number would be "significant."
The president has repeatedly said he is confident the United States can meet the self-imposed deadline to begin bringing U.S. troops back from Afghanistan without compromising Afghan security, though military commanders and government officials have raised concern about the readiness of Afghan security forces.
"We have made great strides toward achieving the objectives laid out in the mission that the president articulated in December of 2009," Carney said. "And he will make his decision based on the need to succeed further in achieving those objectives and to transfer authority gradually, security authority, over to the Afghan national security forces, with an eye to the fact that, as agreed to by NATO in Lisbon, we will eventually transfer full security lead over to the ANSF in 2014."
Nearly three-quarters of Americans polled this month said they support the United States pulling some or all of its forces from Afghanistan.
That figure jumped 10 points since May, likely as a result of the death of Osama bin Laden, pollsters said.
The CNN/Opinion Research Corp. poll was conducted June 3 through June 7, with 1,015 adult Americans questioned by telephone. The survey's overall sampling error is plus or minus 3 percentage points.
CNN's Barbara Starr contributed to this report.