KABUL, Afghanistan (AP) - U.S. Gen. David Petraeus, whose signature counterinsurgency strategy has yet to deliver a safer Afghanistan and push the Taliban to reconcile with the country's Western-allied government, handed over command of international forces here on Monday.

As he heads for his new job as director of the CIA, he relinquished his post to Marine Gen. John Allen, known for helping turn Sunni insurgents against al-Qaida in Iraq. Allen will be tasked with the overseeing the start of the American troop withdrawal from the country after a decade-long war.

Allen, who was promoted to a fourth star as he took command of about 130,000 U.S. and NATO troops, has said he supports President Barack Obama's plan to withdraw a third of the U.S. forces in Afghanistan by next year. But Allen told a Senate hearing last month that the schedule set by Obama was more aggressive than the military had anticipated. Obama did not set a minimum number of troops to be pulled out this month, but required only that 10,000 be gone by the end of the year and that another 23,000 be back home by September 2012.

Allen said the drawdown of U.S. forces that started earlier this month and the transition of some areas to Afghan control this week does not mean that international forces are easing up in their campaign to defeat the Taliban insurgency.

"It is my intention to maintain the momentum of the campaign," Allen said at the handover ceremony in the Afghan capital. He acknowledged, however, that the fight won't be easy.

"There will be tough days ahead. I have no illusions about the challenges," Allen said.

Before taking over from Petraeus, Allen had been serving as the deputy commander at U.S. Central Command in Tampa, Florida. He is best known for his role in the stewardship of the Anbar Awakening - the ultimately successful campaign by U.S. forces in western Iraq to encourage Sunni tribesman to turn against al-Qaida and align with American forces.

There have been fears in Afghanistan that the U.S. decision to draw down its forces could lead to a precipitous withdrawal of other foreign troops. Foreign forces are expected to gradually hand over control of Afghanistan to government forces and end their combat role by the end of 2014.

Afghan Defense Minister Abdul Rahim Wardak said he hoped Petraeus' appointment to the role of CIA director will temper calls for a quick withdrawal of U.S. forces and funding.

"His broad intellect, his unmatched experiences and knowledge of the ground realities will make him a counterbalance to all those shortsighted, politically inspired isolationists and the groups of Beltway bandits, and U.S. national security councils," Wardak said. "Any wavering of the resolve or premature drawdown and exit strategy will put in jeopardy all that we have achieved."

Petraeus steps down at a time when violence has again spiked, with insurgents carrying out attacks against high-profile Afghans - including the assassination last week of President Hamid Karzai's powerful half brother and the slaying of a close Karzai aid on Sunday.

As Petraeus departs, it is unclear whether his counterinsurgency strategy - with an emphasis on protecting the local population and decisive strikes against insurgents - has made Afghanistan any safer. Violent attacks have continued, though international military officials argue they are not as widespread or as intense as they would have been otherwise.

His commanders in Afghanistan have employed a strategy that brought some success in Iraq - coupling military force with an ambitious, troop-intensive plan to push insurgents from their strongholds so the local government could build a system of services and institutions to win the loyalty of the people.

It hoped to create the necessary groundwork for a process of reconciliation and reintegration to encourage insurgents to re-enter Afghan society.

But the plan has been costly, with the United States now spending about $10 billion a month to fund the effort in Afghanistan. Some of his detractors have argued that a more aggressive special operations-centered counterterrorism strategy may be more effective.

In his farewell address, Petraeus said that despite progress made in southern Afghanistan, there was still much work ahead for his replacement.

"Even as we note the hard-fought progress of the past year and commence the transition process, we should be clear-eyed about the challenges ahead," he said, adding that Afghan and coalition forces "are clearly engaged in a tough fight."

He said the campaign against the insurgents was made even more difficult "when the enemy can exploit sanctuaries outside the country," a parting shot at neighboring Pakistan. The military has often accused Islamabad of not doing enough to fight insurgents taking refuge in Pakistan's lawless tribal areas along the border. That fight, along with America's fractured relationship with Pakistan, will be one of Petraeus' key issues as he takes over as director of the Central Intelligence Agency.

"The progress you have made has not been without sacrifice. There have been tough fights, tough losses along the way, setbacks as well as successes," Petraeus said. He added that he was departing "encouraged by the progress, aware of the hard work that lies ahead and hopeful for the future."

Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, lauded Petraeus's work but also said that "a lot of hard work, deadly work remains before us."

He said that during the past year under Petraeus "I have never seen our progress more real and our prospects more encouraging."

The insurgents, Mullen said, have "been dealt heavy blows over the last year. They have been pushed out of sanctuaries, they have been denied influence over local populations, they have been hounded and hunted, their leaders killed or captured by the score, their resources diminished and their training disrupted."

Petraeus, who is retiring from the military, and American officials in the U.S. have trumpeted success in reclaiming Taliban strongholds in southern Afghanistan and training Afghan security forces as signs that they are finally making progress toward peace in Afghanistan. But violent attacks have continued, including a number of high-profile assaults and assassinations in recent weeks.

On Monday morning, a bomb killed three international service members in the east, NATO said in a statement. It did not provide nationalities or further details. Most of the troops in the east are American.

At least 37 international forces have been killed so far this month in Afghanistan.

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