WASHINGTON — President Barack Obama on Wednesday will unveil an Afghanistan drawdown plan that is expected to call for the withdrawal of the 33,000 U.S. troops deployed in last year’s surge by the end of 2012, U.S. defense officials said.

An initial reduction of 5,000 troops would take place this year, followed by another 5,000 soldiers next spring, with the remainder expected to come out by December 2012, said a person with knowledge of the plan, who couldn’t be named because the plan hasn’t been made public. The drawdown’s pace would be dictated by the rate at which Afghan security forces could replace the American unit s.

Some 67,000 U.S. forces would remain in Afghanistan after the expected reductions. Most would leave by the end of 2014, when plans call for the Afghan government to assume full responsibility for the country’s security.

Obama’s decision reflects the rising opposition to the war in both political parties and among a majority of Americans weary of a decade of foreign conflict and unhappy over the sluggish U.S. economic recovery, high unemployment and growing federal budget deficit.

The pressure for a withdrawal intensified with the killing of Osama bin Laden by U.S. Navy SEALs in a May 2 raid on the al-Qaida leader’s hideout near the Pakistani capital of Islamabad. Finally, some U.S. officials and commanders question how much has been achieved in Afghanistan since the 2001 U.S. invasion.

By announcing a withdrawal of all 33,000 U.S. troops deployed in the surge, Obama could claim success for the war strategy that he unveiled in December 2009 as he campaigns for a second term.

“Politically, [Obama] knows the war is extremely unpopular, so he wants to run saying, ‘I kept my promise,’ “ said Christopher Preble of the Cato Institute, a libertarian research center. “His hope is that the public will not dwell on the fact that there would be more troops in Afghanistan at the start of the second Obama administration, if he gets re-elected, than when took office in  January 2009.”

There are some 40,000 other foreign soldiers of the U.S.-led NATO peacekeeping force in Afghanistan. Britain and Germany — the largest contributors after the U.S. — are expected to unveil troop reductions at a ratio similar to that announced by Obama, U.S. defense officials said.

The plan would carry considerable risks. Foremost is whether the Afghan military and police will be capable of taking over security in the key areas of the Taliban’s southern strongholds of Kandahar and Helmand provinces from which U.S. and British troops would be withdrawn.

Moreover, a major drawdown could hinder efforts by the U.S., its allies and Afghan President Hamid Karzai to begin formal talks on a peace accord with the Taliban and allied groups if the insurgents believe they will be facing weaker international forces.

In announcing his war strategy in December 2009, Obama pledged to begin a U.S. troop withdrawal next month. He has been reviewing options presented to him last week by the commander of U.S.-led international forces, Army Gen. David Petraeus.

“He’s finalizing his decision,” White House spokesman Jay Carney said Monday.

A White House official, who requested anonymity in order to discuss the issue, said that Obama would unveil his drawdown plan in Washington on Wednesday. He declined to discuss any details, including the venue at which Obama would make the announcement.

U.S. defense officials said they expected the president to announce a withdrawal by the end of next year of the 33,000 troops deployed in the surge, mostly in southern Afghanistan, last year.

This year’s 5,000-strong reduction, according to the person with knowledge, would be achieved by cancelling the deployment set for next month of a 3,000-strong brigade combat team. Another 2,000 support troops currently in Afghanistan would not be replaced, he said.

The president also plans to cancel the deployment next spring of a second 3,000-strong brigade combat team and an additional 2,000 support troops.

Obama is expected to announce the two deployment cancellations during a visit to Fort Drum, N.Y., scheduled for Thursday.

Afghan troops and police would fill in for the U.S. troops pulled out of Helmand and Kandahar provinces.

Other U.S. units due to replace soldiers sent in the first phase of the surge would be sent to reinforce NATO soldiers striving to crush the insurgency in southeastern provinces bordering Pakistan, where the Taliban and allied groups maintain sanctuaries.

Obama’s core goal is to prevent the Taliban and allied militants from retaking power in Afghanistan and allowing al-Qaida to reclaim a sanctuary from which the terrorist network can plot attacks against the U.S. and its allies.

Following bin Laden’s death, some Obama aides, anxious over the president’s re-election prospects, have been urging him to approve a major U.S. troop withdrawal, and to rely more heavily on U.S. special forces and drone aircraft to strike Taliban and al-Qaida leaders and mid-level commanders.

But retiring Defense Secretary Robert Gates, Petraeus and other senior U.S. commanders have counseled “responsible” reductions at a cautious pace, contending that military pressure must be maintained on the insurgents through the summer of 2012 to compel them to negotiate.

“Some at the Pentagon believe the longer we stay, the more likely there will be a political solution,” said Preble, of the Cato Institute.

Gates and Petraeus have warned that the progress achieved by surge troops in reclaiming southern areas once dominated by the Taliban is “fragile and reversible.”