"The 30,000 additional troops that I am announcing tonight will deploy in the first part of 2010 - the fastest pace possible - so that they can target the insurgency and secure key population centers," he will say in a primetime speech from West Point, according to excerpts released by the White House. "They will increase our ability to train competent Afghan Security Forces, and to partner with them so that more Afghans can get into the fight. And they will help create the conditions for the United States to transfer responsibility to the Afghans."
"Taken together, these additional American and international troops will allow us to accelerate handing over responsibility to Afghan forces, and allow us to begin the transfer of our forces out of Afghanistan in July of 2011," the president plans to say. "Just as we have done in Iraq, we will execute this transition responsibly, taking into account conditions on the ground. We will continue to advise and assist Afghanistan's Security Forces to ensure that they can succeed over the long haul. But it will be clear to the Afghan government - and, more importantly, to the Afghan people - that they will ultimately be responsible for their own country."
A senior administration official stressed in a conference call with reporters Tuesday afternoon that that the July 2011 date marks the beginning of a process that does not have a defined endpoint. The full withdrawal of troops, the official said, will depend on conditions on the ground.
The president will also stress that the effort in Afghanistan is an "international effort" that requires contributions from other countries.
"I have asked that our commitment be joined by contributions from our allies," he will say. "Some have already provided additional troops, and we are confident that there will be further contributions in the days and weeks ahead. Our friends have fought and bled and died alongside us in Afghanistan. Now, we must come together to end this war successfully. For what's at stake is not simply a test of NATO's credibility - what's at stake is the security of our Allies, and the common security of the world."
The rough outlines of a withdrawal plan will be part of the revamped Afghanistan strategy that Mr. Obama is announcing in a speech at 8:00 p.m. Eastern Time. He will tell Americans his planned accelerated war escalation would have the first Marines there as early as Christmas, according to senior administration officials.
With the full complement of troops to be deployed by next summer, the heightened pace of Mr. Obama's military deployment in the 8-year-old war would appear to match the 2007 troop surge in Iraq, which rushed 20,000 combat forces to quell violence there. The Afghan surge would similarly aim to reverse Taliban gains and secure population centers in the volatile south and east parts of the country.
In his primetime speech to the nation, Mr. Obama will tie the escalation to an exit strategy, laying out a rough timeframe for when the main U.S. military mission would end, and outline plans to accelerate handing over security responsibilities to Afghan forces.
Mr. Obama will try to sell a skeptical public on his bigger, costlier war plan by coupling the large new troop infusion with an emphasis on stepped-up training for Afghan forces that he says will allow the U.S. to leave.
Public opinion in this country has become increasingly divided over American participation in the stalemated war.
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The new infusion of troops had been envisioned to take place over a year, or even more, because force deployments in Iraq and elsewhere make it logistically difficult, if not impossible, to go faster.
Instead, Mr. Obama directed his military planners to make the changes necessary to speed up the Afghanistan additions, officials said, speaking on condition of anonymity because the details had not yet been announced. They said the option the president has chosen gets more troops into Afghanistan faster than any other option that had been presented to him.
Military officials said at least one group of Marines is expected to deploy within two or three weeks of Obama's announcement, and would be in Afghanistan by Christmas. Larger deployments wouldn't be able to follow until early in 2010.
The initial infusion is a recognition by the administration that something tangible needs to happen quickly, officials said. The quick addition of Marines would provide badly needed reinforcements to those fighting against Taliban gains in the southern Helmand province, and could lend reassurance to both Afghans and the U.S. public.
Thirty thousand more troops is 10,000 fewer than Gen. Stanley McChrystal, the commander in Afghanistan, requested, reports CBS News correspondent David Martin. The president hopes to make up at least some of the difference with .
"I think NATO will come through with a couple thousand and so I think we'll still be somewhat short of what Gen. McChrystal proposed," Michael O'Hanlon of the Brookings Institution told CBS News.
On a conference call with reporters this afternoon, senior administration officials said that NATO would "step forward with additional contributions of troops," though they did not say how many. There are currently 40,000 troops from countries other than the United States in Afghanistan, along with 68,000 U.S. troops.
Martin reports that the commandant of the Marine Corps has said his troops will among be the first in - about 9,000 into the Taliban heartland in Southern Afghanistan. It was not immediately clear whether that contingent of 9,000 would be deployed by the end of 2009, or would be staggered.
Watch CBS News' David Martin on Obama's Plans
In Kabul, Lt. Gen. William B. Caldwell, the new head of a U.S.-NATO command responsible for training and developing Afghan soldiers and police, said Tuesday that although the groundwork is being laid to expand the Afghan National Army beyond the current target of 134,000 troops, to be reached by Oct. 31, 2010, no fixed higher target is set.
There is a notional goal of eventually fielding 240,000 soldiers and 160,000 police, but Caldwell said that could change.
"Although that is a goal and where we think it could eventually go to, it's not a hard, firm, fixed number," he said in a telephone interview with The Associated Press.
Mr. Obama began rolling out his decision Sunday night, informing key administration officials, military advisers and foreign allies in a series of private meetings and phone calls that stretched into Monday. In the past 24 hours he has spoken to Afghan President Hamid Karzai, Pakistan President Asif Ali Zardari and others about his plans.
Mr. Obama's announcement comes near the end of a year in which the war has worsened despite Mr. Obama's previous infusion of 21,000 forces.
With U.S. casualties in Afghanistan sharply increasing and little sign of progress, the war Mr. Obama once liked to call one "of necessity," not choice, has grown less popular with the public and within his own Democratic party. In recent days, leading Democrats have talked of setting tough conditions on deeper U.S. involvement, or even staging outright opposition.
Mr. Obama also deliver a deeper explanation of why the U.S. must continue to fight more than eight years after the war's start in his address, emphasizing that Afghan security forces need more time, more schooling and more U.S. combat backup to be up to the job on their own. He will make tougher demands on the governments of Pakistan and, especially, Afghanistan, and will provide a fresh path toward disengagement.
In Afghanistan, rampant government corruption and inefficiency have made U.S. success much harder. Mr. Obama was expected to place tough conditions on Karzai's government, along with endorsing a stepped-up training program for the Afghan armed forces along the outline recommended this fall by U.S. trainers.
The displeasure on both sides of the aisle was likely to be on display when congressional hearings on Mr. Obama's strategy get under way later in the week on Capitol Hill.
Mr. Obama briefed dozens of key lawmakers Tuesday afternoon, just before he left the White House for the speech against a military backdrop at West Point.
Military officials said the speech is expected to include several references to Iraq, where the United States still has more than 100,000 forces. The strain of maintaining that overseas war machine has stretched the Army and Marine Corps and limited Mr. Obama's options.
You can watch the speech on your CBS station at 8 p.m. ET or online at CBSNews.com.