— The last of the 33,000 “surge” troops President Obama ordered to Afghanistan in December 2009 have left the country, the Pentagon announced Friday, just ahead of a Sept. 30 deadline.

The number of U.S. troops in the war zone now stands at 68,000, Secretary of State Leon E. Panetta told reporters traveling with him during a week-long visit to the Asia-Pacific region. The troop count is down from a peak of 101,000 U.S. forces last year and marks the end of a critical phase in Obama’s war strategy.

“There’s no question there will continue to be difficult days ahead in this campaign,” Panetta said at a news conference in Auckland, where he was making a visit, in part, to thank New Zealand for its contribution of about 180 troops to the NATO-led coalition in Afghanistan. “But this is an opportunity to recognize that the surge did accomplish its objectives.”

Obama’s strategy has been tested in recent months by the resilience of the Taliban-led insurgency. The U.S. military has also struggled to contain a rash of insider attacks in which uniformed Afghan soldiers and police officers have fired upon their U.S. trainers, disrupting joint operations and undermining the U.S. plan to hand over security responsibilities to the Afghans.

U.S. and NATO commanders announced this week that they would sharply scale back joint patrols and training operations because of their inability to stanch the insider attacks, calling into question a core part of the military strategy.

The drawdown of U.S. forces is in keeping with Obama’s timetable to pull out all conventional combat forces by the end of 2014. U.S. commanders have said that some special operations forces and trainers could remain in Afghanistan after that, but they have not specified how many.

Panetta said the current troop levels are sufficient. He said U.S. forces would continue to focus on training the Afghan army and police, and prevent the Taliban from regaining territory.

“I think we are on track,” he told reporters. He said that Marine Gen. John Allen, the commander of U.S. and NATO forces in Afghanistan, had assured him that the military strategy remained sound.

“Right now, he is saying that he has the force in place to accomplish that mission,” Panetta said.