WASHINGTON - President Obama said he would change direction in the war in Afghanistan if by the end of 2010 his newly set strategy was not working and the U.S. military was not on course "in terms of securing population centers" from Taliban militants.

The president also disputed the impression among some observers that he was overly analytical and emotionally detached in his Dec. 1 speech ordering 30,000 more soldiers and Marines into the eight-year-old war. The decision "hit me in the gut" emotionally more than any, he said.

After doubling the U.S. force in Afghanistan in March, just two months after taking office, Obama raised the stakes further by ordering a nearly 50 percent troop increase in a speech at the U.S. Military Academy at West Point, N.Y.

He issued the orders even as support for the war is crumbling among the public and opposed by many fellow Democrats in Congress.

"You know, that was actually, probably, the most emotional speech that I've made, in terms of how I felt about it, because I was looking out over a group of cadets, some of whom were going to be deployed in Afghanistan, and potentially some might not come back," Obama told CBS's 60 Minutes, in an interview taped last Monday for broadcast last night.

Obama also answered critics who saw ambiguity in his ordering the big troop increase while then saying they would begin coming home in July 2011.

That is the date when U.S. military forces plan to start handing security responsibility to Afghan soldiers and police who would undergo intensive recruitment and training.

"We then start transitioning into a drawdown phase," Obama repeated, noting that specifics were conditional. "How many U.S. troops are coming out, how quickly, will be determined by conditions on the ground."

And he gave himself a loophole.

"If the approach that's been recommended doesn't work, then yes, we're going to be changing approaches," he said. Obama quickly added that the deadline was necessary to alert the Afghan leadership that the United States was not going to make Afghanistan an American "protectorate."

Gen. Stanley McChrystal, the U.S. commander in Afghanistan, agreed to the mission of securing the population, saying success would mean "over time they [the Taliban fighters] become irrelevant and ineffective."

McChrystal had sought 40,000 additional troops for the war against the Taliban and its al-Qaeda allies. Obama settled on 30,000. Most of the shortfall between what McChrystal sought and what Obama approved is expected to be made up by NATO and other allies.

Obama and McChrystal said the idea was to mimic - to some extent - the Bush administration's troop increase in Iraq that deflated the Sunni insurgency there by bringing many of its fighters into the U.S. fight to defang the al-Qaeda forces.

Many Sunnis, the minority Muslim sect in Iraq, had joined forces with al-Qaeda after U.S. forces ousted dictator Saddam Hussein. He was a Sunni, and his departure pushed the Sunnis from their traditional hold on power.

The president also once again put Pakistan on notice that it was going to have to do more against its own Taliban militants and al-Qaeda.

The organization's leader, Osama bin Laden, and his chief lieutenants and many fighters fled to the largely ungoverned and mountainous regions of Pakistan after the United States invaded Afghanistan in 2001, shortly after the Sept. 11 terrorist attacks.

"In order for us to eradicate the problem, to really go after al-Qaeda, in an effective way, we are going to need more cooperation from Pakistan," Obama said. "There is no doubt about that."

Obama also took a swipe at the Bush administration.

"One of the mistakes that was made over the last eight years is for us to have a triumphant sense about war," Obama said. "There was a tendency to say 'We can go in. We can kick some tail. This is some glorious exercise.' When, in fact, this is a tough business."