Washington (CNN) -- In his State of the Union speech Tuesday, President Barack Obama will announce that by this time next year, 34,000 U.S. troops in Afghanistan will have returned home, according to sources with knowledge of the president's speech.
The move will reduce the number of U.S. forces in the country by more than half. There are now about 66,000 U.S. troops in Afghanistan.
A Washington Post poll out Tuesday morning shows that 80% of registered voters support the president's policy to end the war in Afghanistan.
In January, Obama met with Afghan President Hamid Karzai in Washington, where they agreed to accelerate the military transition in Afghanistan. Afghan forces will take the lead in combat missions throughout the country starting in the spring, instead of mid-year, as was previously expected.
The White House has been considering a range of troop levels to remain in Afghanistan once the combat mission officially ends at the end of 2014, from as many as 15,000 troops to none at all.
Those options were submitted by Gen. John Allen, who until recently was the top U.S. commander in Afghanistan. Allen's final days as the top commander were marred by an investigation linked to the sex scandal that prompted the resignation of David Petraeus as CIA director.
Allen was cleared of allegations that he wrote potentially inappropriate e-mails to a woman involved in the scandal. He is now the nominee to become the top NATO commander and was replaced in Afghanistan this week by Marine Gen. Joseph Dunford.
More troop reductions ahead
A senior administration official told CNN Tuesday that in addition to bringing home 34,000 U.S. troops by February 2014, more reductions will continue through the end of next year as Afghans take full responsibility for their security.
The United States and its partners in the war in Afghanistan have "struck devastating blows against al Qaeda, and Afghan forces continue to grow stronger, with 352,000 now in training or on duty," the official said.
Afghan forces are leading nearly 90% of operations across Afghanistan, and by this spring they'll take the lead across the entire country, the official said.
The U.S. and the International Security Assistance Force, known asISAF, will continue to step back to train, advise and assist Afghan forces, the official said, explaining that that means the United States will no longer be leading combat operations.
"By the end of 2014, we will responsibly bring our war in Afghanistan to a close," the official said, adding that Obama made his decision "based on the recommendations of the military and his national security team," consultations with Karzai and "international coalition partners."
Afghans in lead but U.S. still there
Also on Tuesday, another U.S. official told CNN's Pentagon correspondent Barbara Starr that the U.S. and NATO alliance will announce that by March, Afghan troops will lead all security in Afghanistan.
That announcement, which was expected to be made this summer, will be made within days, the source told Starr.
While the move puts Afghan units in the fore of operations, U.S. troops will still be directly involved in combat for months to come, the official said. And even with Afghans in the lead, U.S. special forces will remain in far flung outposts partnering with Afghan units.
A new general in charge
Dunford will oversee the final two years of the war and the withdrawal of nearly all troops.
On Sunday, at a change-of-command ceremony in Kabul, Dunford remarked on the job ahead.
"Today is not about change, it's about continuity," he said, alongside Allen and other senior NATO and Afghan officials.
"I'll endeavor to continue the momentum of the campaign and support the people of Afghanistan as they seize the opportunity for a brighter future."
Dunford has a reputation among Marines as a thoughtful, calm leader, with more than 22 months under his belt of commanding troops in Iraq.
These changes come amid debate about impending budget cuts that some say would have grave consequences for the military.Sequestration is a series of automatic, across-the-board cuts to government agencies, totaling $1.2 trillion over 10 years. The cuts would be split 50-50 between defense and domestic discretionary spending.
More than $500 billion would be cut from the Defense Department and other national security agencies, with the rest cut on the domestic side in areas such as national parks, federal courts, the FBI, food inspections and housing aid.
Outgoing Defense Secretary Leon Panetta has been a harsh critic of the cuts.
"For those of you who have ever seen 'Blazing Saddles,'" he said in a recent speech at Georgetown University, there "is the scene of the sheriff putting the gun to his head in order to establish law and order. That is sequestration."