BISHKEK, Kyrgyzstan — Kyrgyzstan today ordered U.S. forces to depart within six months from an air base key to military operations in Afghanistan, complicating plans to send more troops to battle rising Taliban and al-Qaida violence.

U.S. Defense Secretary Robert Gates said, however, he believed the base was not a "closed issue." The U.S. has said it would consider paying more rent to keep the base open.

Pakistani militants have stepped up attacks on convoys traveling the primary supply route to Afghanistan in recent months pushing U.S. officials to secure alternative, northern routes through Central Asia.

The U.S. announced a small victory in that hunt Friday — saying neighboring Uzbekistan had granted permission for the transit of non-lethal cargo to Afghanistan.

"I continue to believe this is not a closed issue, and that there remains the potential to reopen this issue," Gates said when asked about the closure of the Manas base. "But we are developing alternative methods of getting resupply and people into Afghanistan."

Washington has received Russian permission for non-lethal cargo to be shipped across Russia. Central Asia's largest country, Kazakhstan, has also agreed.

But there's been uncertainty about how cargo would get across former Soviet Central Asia, particularly given uneasy relations between Washington and the country straddling the easiest route into Afghanistan — Uzbekistan, one of the most politically repressive of the former Soviet states.