CAMP DWYER, Afghanistan — US defense chief Leon Panetta visited troops in southern Afghanistan Sunday as part of his first trip to the country since taking up his post and ahead of a withdrawal of some US forces.

The former CIA director, who took office on July 1 to replace Robert Gates, flew into Helmand province, where mostly US forces are battling the nearly decade-long Taliban insurgency.

His visit comes as commanders prepare to hand over seven NATO-held areas to Afghan control starting in mid-July, but amid widespread doubt over the ability of Afghan forces to take full responsibility for their own security.

Panetta said Saturday that the focus of his trip would be the handover to Afghan-led security, acknowledging that there remained "a lot more work to do in terms of being able to transition the responsibility to them".

"The key to success in Afghanistan is the ability to successfully transition to the Afghans," he said after holding high-level talks in the capital Kabul.

"That means they have to develop a capable military, a capable police force, capable local militias that are going to be able to maintain stability. That's the key and that's the area we're gonna focus on."

US President Barack Obama has announced that 10,000 US forces will leave Afghanistan this year and another 23,000 by the end of September 2012, ahead of a full withdrawal of foreign forces in 2014.

The new Pentagon chief was to visit a field hospital in Helmand and speak to US marines credited with reversing the momentum of the Taliban in the province, one of the most dangerous parts of the war-ravaged country.

General David Petraeus, the top commander in Afghanistan who is due to leave his post this month, said the overall number of insurgent attacks on Afghan and foreign forces was down, defying the expectations of intelligence analysts.

Attacks had decreased "a few percent" for May and June, the beginning of the traditional annual fighting season, said Petraeus, although he said the number of home-made bomb explosions had risen.

"So you have the first two months of comparison with the previous year is actually a reduction. July is trending that way. That is very significant," he told reporters in the Afghan capital Saturday.

Intelligence analysts had predicted a rise in insurgent attacks of 18 to 30 percent on last year, Petraeus said, while he cautioned that it was too early to declare the insurgency had been significantly hit.

Petraeus is due to take up Panetta's old position at the CIA in September.

US-led coalition forces have been fighting the Taliban-led insurgency in Afghanistan since their invasion in late 2001 in the wake of the September 11 attacks orchestrated by Osama bin Laden.

Panetta credited the war with disrupting bin Laden's Al-Qaeda network and said Saturday that since US forces killed him in Pakistan in May, 10-20 key leaders had been identified across Pakistan, Yemen, Somalia and north Africa.

He declared the strategic defeat of Al-Qaeda "within reach".

"We've been able to disrupt, dismantle Al-Qaeda. We've been able to in many ways return Afghanistan to itself instead of having the Taliban run that country," he said.

Petraeus later told reporters that a "small element" of Al-Qaeda remained in Afghanistan, mostly in the rugged regions of Kunar and Nuristan.