US Pentagon Press Secretary Maj Gen Pat Ryder said on Thursday that the US plans to "reposition" some of its military forces from Chad, but did not say how many would be affected or where they would be moved to.

"This is a temporary step as part of a ongoing review of our security cooperation, which will resume after Chad's 6 May presidential election," he said.

The announcement follows Chad's air force chief ordering the US to halt activities at an airbase near the capital, N'Djamena, earlier this month, Reuters news agency reported.

Gen Ryder also said that talks with Niger's ruling military junta, the National Council for the Safeguard of the Homeland (CNSP), began on Wednesday and are aimed at ensuring "an orderly and responsible withdrawal of US forces" from the country.

The US has relied on Niger as its primary base for monitoring regional jihadist activity.

But the ruling junta, in power since last July, ended a military agreement that allowed US personnel to be deployed in the country and kicked out French troops.

The moves are the latest in Niger's efforts to cut links with the West.