The top U.S. defense official says a new agreement might be sought with Kyrgyzstan to avoid the eviction of U.S. forces from key military base that supports western troops in Afghanistan.

Kyrgyzstan on Friday ordered U.S. forces to leave the Manas air base within six months after Kyrgyz President Kurmanbek Bakiyev signed the decision into law.

During a NATO meeting in Poland, U.S. Defense Secretary Robert Gates said he believed the issue was not "closed," and that the U.S. would try to reach a new agreement with Kyrgyzstan. As an alternative, Gates said the U.S. is considering other supply routes.

Manas Air Base is currently the only U.S. military supply route in Central Asia.

A top U.S. military officer said Tajikistan and Uzbekistan have agreed to allow the transit of non-lethal U.S. cargo through their territory to Afghanistan.

Rear Admiral Mark Harnitchek said the United States planned to send 50 to 200 containers a week to Afghanistan through the two countries.

Washington has also received permission from Russia and Kazakhstan to send supplies to Afghanistan by rail.

Kyrgyz President Bakiyev had complained that Washington was not paying enough rent for the base. He announced plans to close it after Russia pledged to give Kyrgyzstan about $2 billion in loans and aid.

Most U.S. and NATO shipments into Afghanistan have been arriving by road through Pakistan, but those convoys have increasingly come under attack from Taliban and al-Qaida militants.

Some information for this report was provided by AFP and AP.