WASHINGTON: President Barack Obama announced on Wednesday a plan to start bringing US troops home from Afghanistan in a significant first step toward ending the long, costly Afghan war.

In a televised address, Obama said he would pull 10,000 troops from Afghanistan by year's end, followed by about 23,000 more by the end of next summer.

Troops will be withdrawn at a steady pace after that, Obama said, as the United States, struggling to repair its global image and fix its weak domestic economy, looks to end a decade of military ventures prompted by the Sept. 11 attacks in 2001.

“Huge challenges remain. This is the beginning - but not the end of our effort to wind down this war,” Obama said.

“America, it is time to focus on nation building at home.”

Obama also vowed the United States will “insist” Pakistan fulfill its promises to counter militant sanctuaries on its soil.

“We will work with the Pakistani government to root out the cancer of violent extremism, and we will insist that it keep its commitments,” he said.

Obama's comments underscored festering tensions between Washington and Islamabad in the wake of a unilateral US raid that killed Al-Qaeda leader Osama bin Laden in his hideout in Pakistan last month.

In blunt language, Obama made clear he was ready to order more assaults against any safe-havens harboring those who aimed to kill Americans.

“For there should be no doubt that so long as I am president, the United States will never tolerate a safe-haven for those who aim to kill us: they cannot elude us, nor escape the justice they deserve,” he said.

Referring to Pakistan, Obama said “no country is more endangered by the presence of violent extremists.”

The US president said his government would “continue to press Pakistan to expand its participation in securing a more peaceful future for this war-torn region.”

News that Obama will pull the entire 'surge' force he sent to Afghanistan in 2010 caps weeks of speculation about the future of US involvement there and could increase friction between Obama and military advisors who have warned about the perils of a hasty drawdown.

Nearly 10 years after the Sept. 11 attacks that triggered the war, US and Nato forces have been unable to deal a decisive blow to the insurgent Taliban.

The Afghan government remains weak and notoriously corrupt and billions of dollars in foreign aid efforts have yielded meager results.

Obama's announcement comes the week after General David Petraeus, the outgoing commander of US and Nato troops in Afghanistan, presented several options for drawing down some of the 100,000 US soldiers there starting in July.

But Obama's move was a more aggressive approach that went beyond the options offered by Petraeus.

The president's decision appears to reflect the competing pressures he faces as he seeks to rein in government spending and halt American casualties without endangering the gains his commanders say they have made across southern Afghanistan.

Outgoing Defense Secretary Robert Gates said he supported Obama's decision, but the plan is unlikely to sit well with the Pentagon's top brass who worry insurgents could regain lost territory and that fighting along Afghanistan's eastern border with Pakistan will intensify.

Jeffrey Dressler, a military analyst at the Institute for the Study of War in Washington, said the Pentagon would have favored a much smaller initial withdrawal.

“But the fact is that the conditions on the ground don't merit any sort of withdrawal -- it's not time to be pulling out a substantive amount of troops,” he said.

“There's a lot that has to be done in the east and you're not out of the woods in the south yet.”

Yet Obama also faces mounting demands from some quarters of the US Congress, impatient with a war that now costs more than $110 billion a year, for a larger initial drawdown.

Even after the withdrawal of the 33,00 US troops, about 70,000 will remain in Afghanistan by the autumn of 2012, more than were there when Obama took office.

SHIFT SINCE BIN LADEN'S DEATHThe debate in Washington has shifted palpably since US special forces killed al Qaeda leader Osama bin Laden in Pakistan last month, which Obama said showed al Qaeda was 'under enormous strain.'

Bin Laden's death has given critics from both parties ammunition to argue that the Obama administration must narrow US goals in desperately poor Afghanistan —focusing on lawless havens insurgents can use to launch attacks.

“We will not try to make Afghanistan a perfect place. We will not police its streets or patrol its mountains indefinitely,” Obama said. “That is the responsibility of the Afghan government.”

Obama said the United States would continue to support efforts to foster a political settlement with the Taliban.

Officials acknowledge a peace deal may be far in the future even if one could be had.

Obama is mindful of the American public's lack of support for the war as he looks to his 2012 re-election campaign.