US Defense Secretary Lloyd Austin has approved a new command structure in Afghanistan that includes the transition of US military mission from warfighting to two new objectives: protecting a continuing US diplomatic presence in Kabul and maintaining liaison with the Afghan military, Pentagon press secretary John Kirby said on Friday.

The plan calls for the top US and NATO forces commander in Afghanistan, Gen. Scott Miller, to transfer his combat authorities to the head of US Central Command, Marine Gen. Frank McKenzie.

"General Miller will remain in theater in coming weeks to prepare for and to complete the turnover of these duties and responsibilities to General McKenzie," Kirby said. "Importantly, General McKenzie will retain all existing authorities as Commander of US Forces in Afghanistan."

He said that Gen. McKenzie will continue to exercise authority over the conduct of any and all counterterrorism operations needed to protect the homeland from threats emanating out of Afghanistan.

The Associated Press reports that a two-star Navy admiral will head a US Embassy-based military office, dubbed US Forces Afghanistan-Forward, to oversee the new mission of providing security for the embassy and its diplomats.

A satellite military office based in Qatar and headed by a US one-star general will be established to administer US financial support for the Afghan military and police, plus maintenance support provided for Afghan aircraft from outside Afghanistan, AP report says.

“A safe, orderly drawdown enables us to maintain an ongoing diplomatic presence, support the Afghan people and the government, and prevent Afghanistan from once again becoming a safe haven for terrorists that threatens our homeland,” Kirby said on Friday.

This comes as the US military has left the Bagram Airfield in central Afghanistan and has handed it over to Afghan National Defense and Security Forces, the Ministry of Defense confirmed on Friday.

At its peak, the airfield, located 69 kilometers north of Kabul in the central province of Parwan, saw more than 100,000 US troops pass through its compound.

The handover of the airfield to Afghan forces shows that last of the roughly 2,500 to 3,500 US troops have left Afghanistan.

Ahead of leaving the base, dozens of trailer trucks loaded with scrap from destroyed vehicles and equipment that belonged to American troops were leaving the Bagram Airfield on a daily basis.

Those who purchase the material say that so far, the scrap has been worth millions of dollars.

Some residents of Bagram said that such equipment should have been handed over to Afghan forces instead of being scrapped by the US military. But US forces have said the equipment will be scrapped so it does not fall into enemy hands.

The Afghan government has said that equipment worth $1 billion will be handed over to the Afghan forces.

Bagram Airfield has been the biggest airbase of the US military in Afghanistan over the last 20 years. US forces started a withdrawal on May 1, a process that is expected to be completed earlier than the given deadline – Sept. 11.