WASHINGTON (AP) — President Barack Obama will map a course for drawing down the nearly 10-year war in Afghanistan Wednesday, when he is expected to set a target of bringing home about 30,000 troops by the end of 2012.

The president is likely to pull out 10,000 troops by the end of this year, administration and Pentagon officials said, and aims to bring another 20,000 home by the end of next year.

But with 100,000 U.S. troops currently in Afghanistan, that drawdown may not be substantial enough to satisfy some lawmakers on Capitol Hill and a war-weary public.

The initial withdrawal is expected to happen in two phases, with 5,000 troops coming home this summer and an additional 5,000 by the end of the year, a senior U.S. defense official said.

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The pace of bringing home the other 20,000 forces was unclear heading into Obama’s primetime address to the nation Wednesday. The White House opted not to give the president’s speech the weight of an Oval Office address. Instead, Obama was to speak for about 10 to 15 minutes from the East Room of the White House.

Obama’s expected blueprint focuses on the 30,000 surge forces he ordered to Afghanistan as part of his 2009 decision to send reinforcements to reverse the Taliban’s battlefield momentum.

The president reached his decision a week after receiving a range of options from Gen. David Petraeus, the top U.S. and NATO commander in Afghanistan. Obama informed his senior national security advisers, including outgoing Defense Secretary Robert Gates and Secretary of State Hillary Rodham Clinton, of his plans during a White House meeting Tuesday.

“The president is commander in chief,” spokesman Jay Carney said. “He is in charge of this process, and he makes the decision.”

The administration has begun briefing NATO allies on its plans. British Prime Minister David Cameron’s office confirmed that officials there have been informed but declined to offer comment, or to make any immediate statement on the plans for about 9,500 British forces in Afghanistan.

The withdrawals would put the U.S. on a path toward giving Afghans control of their security by 2014 and ultimately shifting the U.S. military from a combat role to a mission focused on training and supporting Afghan forces.

The Obama administration has said its goal in continuing the Afghanistan war is to blunt the Taliban insurgency and dismantle and defeat al-Qaida, the terror network that used the country as a training ground for the Sept. 11, 2001, attacks on the U.S. As of Tuesday, at least 1,522 members of the U.S. military had died in Afghanistan as a result of the U.S. invasion of Afghanistan in late 2001, according to an Associated Press count.

The U.S. and its allies have set Dec. 31, 2014, as a target date for ending the combat mission in Afghanistan.

A reduction this year totaling 10,000 troops would be the rough equivalent of two brigades, which are the main building blocks of an Army division. It’s not clear whether Obama’s decision would require the Pentagon to pull out two full brigades or, instead, withdraw a collection of smaller combat and support units with an equivalent number of troops.

If Obama were to leave the bulk of the 30,000 surge contingent in Afghanistan through 2012, he would be giving the military another fighting season — in addition to the one now under way — to further damage Taliban forces before a larger withdrawal got started. It also would buy more time for the Afghan army and police to grow in numbers and capability.

Under that scenario, the emphasis in U.S.-led military operations is likely to shift away from troop-intensive counterinsurgency operations toward more narrowly focused counterterrorism operations, which focus on capturing and killing insurgents.

Afghan security forces and judicial institutions are expected to take up many aspects of the counterinsurgency fight by establishing the rule of law and respect for government institutions, U.S. officials in Afghanistan said Tuesday.

In recent speeches, Afghan President Hamid Karzai has criticized American forces, suggesting his ally is in danger of becoming an occupying force. He has even threatened action against international forces that conduct airstrikes and has accused allies of undermining and corrupting his government.

Yet there are concerns in his country about the withdrawals. Some of the areas slated to transition to Afghan control have been struck by attacks in recent weeks despite assertions by Karzai that peace talks have started between the U.S., his Afghan government and Taliban emissaries. Publicly, the Taliban say there will be no negotiations until foreign troops leave Afghanistan.

The transition to full Afghan control will begin in earnest on July 20 in five provincial capital cities and two provinces. The provincial capitals identified for transition are Lashkar Gah in Helmand province, plus capitals from provinces in the west, east and north and most of Kabul, the nation’s capital. The largely peaceful northern provinces of Bamyan and Panjshir will also start to transition to Afghan control.

Some U.S. military commanders have favored a more gradual reduction in troops than Obama is expected to announce Wednesday night, arguing that too fast a withdrawal could undermine the fragile security gains.

But other advisers have backed a more significant withdrawal that starts in July and proceeds steadily through the following months. That camp believes the slow yet steady improvements in security, combined with the killing of Osama bin Laden and U.S. success in dismantling much of the al-Qaida network in the country, give the president an opportunity to make larger reductions this year.

Obama previously has said he favors a “significant” withdrawal beginning in July, his self-imposed deadline for starting to bring U.S. troops home. Aides, however, have never quantified that statement.

Pressure for a substantial withdrawal has been mounting from the public and Congress. Even Gates, who has said he favored a “modest” withdrawal, said Tuesday that Obama’s decision needed to incorporate domestic concerns about the war.

“It goes without saying that there are a lot of reservations in the Congress about the war in Afghanistan and our level of commitment,” Gates said during a news conference at the State Department. “There are concerns among the American people who are tired of a decade of war.”

According to an Associated Press-GfK poll last month, 80 percent of Americans say they approve of Obama’s decision to begin withdrawal of combat troops in July and end U.S. combat operations in Afghanistan by 2014. Just 15 percent disapprove.

On Capitol Hill, even the more moderate or conservative members of his party, such as Sen. Bob Casey of Pennsylvania and Sen. Joe Manchin of West Virginia, are pressing for significant cuts and a shift in mission.

“The question the president faces — we all face — is quite simple: Will we choose to rebuild America or Afghanistan? In light of our nation’s fiscal peril, we cannot do both,” Manchin said Tuesday.

Sen. Carl Levin, D-Mich., chairman of the Senate Armed Services Committee, said improved conditions in Afghanistan would permit Obama to withdraw at least 15,000 troops by the end of the year.

Obama aides have sidestepped questions about what role the cost of the war in Afghanistan played in Obama’s decision, saying only that the president was focused on meeting the goal of transferring security by 2014.

Following the announcement on the drawdown, Obama will visit troops Thursday at Fort Drum, the upstate New York Army post that is home to the 10th Mountain Division, one of the most frequently deployed divisions to Afghanistan.

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Associated Press writers Lolita C. Baldor, Matthew Lee and Donna Cassata in Washington and Solomon Moore in Kabul, Afghanistan, contributed to this report.

Copyright 2011 The Associated Press.