U.S. President Barack Obama speaks about the war in Afghanistan at the U.S. Military Academy at West Point, N.Y., on Tuesday. (Charles Dharapak/Associated Press)

President Barack Obama has ordered 30,000 more U.S. troops to be deployed in Afghanistan — but he also pledged Tuesday to begin withdrawing American forces in about 18 months, beginning in July 2011.

In a televised prime-time speech at the U.S. Military Academy at West Point, N.Y., the president said "our security is at stake" and his new policy is designed to "bring this war to a successful conclusion."

The troop buildup, which will cost $30 billion US for the first year alone, will begin almost immediately with the first marines in place by Christmas.

"We must deny al-Qaeda a safe haven," Obama said "We must reverse the Taliban's momentum. ... And we must strengthen the capacity of Afghanistan's security forces and government."

The additional forces will be sent at "the fastest pace possible so that they can target the insurgency and secure key population centres," [and their destination would be] "the epicentre of the violent extremism practised by al-Qaeda," Obama said.

Cadets listen to Obama's speech at West Point. (Julie Jacobson/Associated Press)

"It is from here that we were attacked on 9/11, and it is from here that new attacks are being plotted as I speak."

It marks the second time in his presidency that Obama has added to the American force in Afghanistan, where the Taliban has recently made significant advances. When he became president last January, there were roughly 34,000 troops on the ground. There now are 71,000.

Most of the new forces will be combat troops, most likely from Fort Drum in New York and Fort Campbell in Kentucky, and marines primarily from Camp Lejeune in North Carolina.

The additional 30,000 troops will include about 5,000 trainers, underscoring Obama's emphasis on preparing Afghans to take over their own security.

'Deliver for the people'

"The days of providing a blank cheque are over," Obama said. The United States will support Afghan ministries that combat corruption and "deliver for the people. We expect those who are ineffective or corrupt to be held accountable," he said.

The additional troops, Obama said, "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."

Drawing on America's experience in Iraq, Obama said a U.S. withdrawal from Afghanistan will be executed 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," Obama said.

In Kabul, Gen. Stanley McChrystal, the top U.S. commander in Afghanistan, said early Wednesday that NATO and U.S. forces will hand over the responsibility of securing Afghanistan to the nation's own security forces "as rapidly as conditions allow."

Demonstrators gather near the U.S. Military Academy at West Point to protest Obama's speech. (Craig Ruttle/Associated Press)

McChrystal made the comments in a statement issued just before Obama's speech.

Obama also leaned heavily on NATO allies and other countries to join in escalating the fight. "We must come together to end this war successfully," he said. "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."

NATO diplomats said Obama was asking alliance partners in Europe to add 5,000 to 10,000 troops to the separate international force in Afghanistan. Indications were the allies would agree to a number somewhere in that range.

The war has even less support in Europe than in the United States, and the NATO allies and other countries currently have about 40,000 troops on the ground.

Canada's military mission to Afghanistan began soon after the attacks on the United States on Sept. 11, 2001. The current mission in Kandahar, which began at the end of 2006, includes 2,800 troops focused around an infantry battle group.

Prime Minister Stephen Harper has repeatedly said he will adhere to a motion passed in Parliament and not extend Canada's military mission beyond 2011.

Since 2002, 133 Canadian soldiers have been killed in the Afghan mission, resulting in the highest per-capita death rate among foreign armies in Afghanistan. One diplomat and two aid workers have also been killed.

Lawrence Cannon, Canada's minister of foreign affairs, welcomed Obama's announcement of additional troops.

"We look forward to furthering our collaboration with the U.S. in order to reach our ultimate and common goal of leaving Afghans an Afghanistan that is better governed, more peaceful and more secure," Cannon said from Brussels, where he will attend a NATO summit meeting.

Sharing common enemy

Turning to Pakistan, Obama said the U.S. and that country "share a common enemy" in Islamic terrorists. Obama says the same "cancer" of terror that hampered Afghanistan has taken root along the border with Pakistan.

His policy will be to strengthen Pakistan's capacity to target terrorists, and he said the U.S. has "made it clear that we cannot tolerate a safe haven for terrorists whose location is known," Obama said.

While the al-Qaeda leadership appears to be bottled up in Pakistan's largely ungoverned tribal regions, the U.S. military strategy of targeted missile attacks from unmanned drone aircraft has yet to flush Osama bin Laden and his cohorts from hiding.

Obama began his much-anticipated speech t by recalling "why America and our allies were compelled to fight a war in Afghanistan in the first place. …We did not ask for this fight," Obama said.

The United States went to war in Afghanistan shortly after the 9/11 al-Qaeda attacks on the United States.

Bin Laden and key members of the terrorist organization were headquartered in Afghanistan at the time, taking advantage of sanctuary afforded by the Taliban government that ran the mountainous and isolated country.

Taliban forces were quickly driven from power, while bin Laden and his top deputies were believed to have fled through towering mountains into neighbouring Pakistan.

With files from The Associated Press