U.S. military operations in Afghanistan will not be affected by the possible closure of a United States' air base in nearby Central Asian country Kyrgyzstan, a U.S. general said on Sunday.

Almost 65,000 foreign troops, mostly from the United States and NATO member countries, are deployed in Afghanistan, locked in a violent struggle against resurgent Taliban-led militants.

On Thursday, former Soviet Republic Kyrgyzstan said it would close a U.S. air base on its soil used to ferry supplies and troops into Afghanistan, but Washington says talks with the Kyrgyz government to keep the Manas base open were ongoing.

"We have many ways of bringing people and equipment into this country and we are not dependent on any one way," said Brigadier General James McConville, deputy commander of support for U.S. and NATO-led forces in eastern Afghanistan.

"The places that we use benefit economically from our presence, and so when our presence goes away those people who are dependent on our economic input will probably be hurt."

But McConville's counterpart responsible for security in east Afghanistan, Brigadier General Mark Milley said on Friday there could be some "fallout" from the closure of the Manas base for the U.S. effort in Afghanistan, but would not give details.

Some 30,000 mainly U.S. troops in east Afghanistan are supplied by convoys using a highway which connects the Pakistani city of Peshawar to a U.S. air base in Bagram, north of Kabul.

Plans to deploy an extra 25,000 U.S. troops in the next 12 to 18 months, which would almost double the number of U.S. soldiers in Afghanistan, would make the need to secure supply routes even more important.

A spate of attacks in the last few months on military supply convoys and depots on this route, and several attacks on the Khyber Pass, have highlighted the need for alternative means of transporting goods to Afghan and foreign forces.

McConville said there were "weeks and months" of supplies left and that "multiple means" including air transport and alternative ground routes were available, including recently-agreed routes from Russia.

"It just gives us another opportunity to access supplies in the country," McConville said, but he declined to say which Central Asian countries the route from Russia would by-pass in order to reach land-locked Afghanistan.