Kyrgyzstan ordered U.S. forces on Friday to depart within six months from an air base key to military operations in Afghanistan, a move complicating plans to send more troops to battle rising Taliban and Al Qaeda violence.

A top U.S. military official said, however, that neighboring Uzbekistan had granted permission for the transit of non-lethal cargo to Afghanistan — a small victory in the hunt for new supply routes.

The U.S. has had a fraught relationship with Uzbekistan, one of the most politically repressive of the former Soviet states. Most of President Islam Karimov's opponents have been sent to jail or into exile. U.S.-based Human Rights Watch has said that Uzbek prison authorities routinely abuse and torture prisoners.

Anger over Western criticism of a crackdown on an uprising in eastern Uzbekistan prompted the government to evict U.S. troops from an air base near the Afghan border in 2005, leaving the Manas air base in Kyrgyzstan as the only U.S. base in Central Asia.

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In recent months, militants have stepped up attacks on convoys traveling through the primary route — Pakistan — pushing U.S. officials to secure alternative, northern routes for Afghan cargo through Central Asia.

The Kyrgyz move to close Manas — a transit point for 15,000 troops and 500 tons of cargo each month heading to Afghanistan — caught the United States by surprise and made the search more urgent .

U.S. officials have said they consider the future of Manas still open for negotiations, indicating there could be talks about the amount paid for maintaining the base.

U.S. Defense Secretary Robert Gates said Thursday that the United States would consider paying more in rent but would not "be ridiculous about it."

Kyrgyzstan's president complained when announcing the closure this month that the United States was not paying enough rent for the base. The announcement came shortly after Russia said it would give $2.15 billion in aid and loans to the impoverished Central Asian nation. U.S. officials suspect that Russia, long wary of U.S. presence in ex-Soviet Central Asia, is behind the decision to shut the Americans out.

"This was not an unexpected move, however we have not received formal notification of the decision from the Kyrgyz foreign ministry," Michelle Yerkin, spokeswoman for the U.S. Embassy in Bishkek, said Friday. "The 180-day clock begins upon formal diplomatic notification."

As part of efforts to secure new routes, Washington received Moscow's permission for non-lethal cargo to be shipped across Russia. Central Asia's largest country, Kazakhstan, has also agreed.

However, there's been uncertainty about how the cargo would get across former Soviet Central Asia, particularly given uneasy relations between Washington and the country straddling the easiest route into Afghanistan — Uzbekistan. The commander of U.S. operations in Afghanistan and Iraq, Gen. David Petraeus, traveled to the Uzbek capital, Tashkent, earlier this week to meet with Karimov.

No details of his visit were released.

But on Friday, U.S. Rear Admiral Mark Harnitchek — a military transportation officer — said that Uzbekistan had reached a deal for cargo to be shipped across its territory.

"We have a tentative agreement with Uzbekistan on transit," he said during a visit to another Central Asian nation that borders Afghanistan, Tajikistan. His comments were shown on Tajik state television.

Some of the goods will be transported from Uzbekistan onward through Tajikistan, which also shares a direct border with Afghanistan, Harnitchek said.

"We plan to move between 50 and 200 containers to Afghanistan through Tajikistan every week," he said.

It was unclear why the cargo would not be shipped directly from Uzbekistan into Afghanistan. U.S. Embassy officials in Uzbekistan declined to comment, as did the Uzbek Foreign Ministry. U.S. Central Command officials could not be immediately located for comment.

President Barack Obama announced earlier this week that he would send 17,000 more U.S. troops to Afghanistan to augment the 33,000 already there.