WASHINGTON (AFP) - US Defence Secretary Ashton Carter on Wednesday indicated the United States would maintain extra troops in Afghanistan beyond the end of next year.

Under current plans, the United States will draw-down its troop numbers by the end of 2016 from about 10,000 currently to a crew of only about 1,000.

Echoing remarks he made at a Nato meeting in Brussels last week, Carter said it was important for the United States "to formulate options for 2016 and beyond and make adjustments to the planned US presence based on current circumstances."

The Obama administration has come under criticism for its planned withdrawal of forces, with opponents saying the move opens up Afghanistan to more attacks by the Taleban, who just two weeks ago captured the city of Kunduz.

A swift response by US-trained Afghan security forces led to an eventual Taleban retreat.

"It's important to say these things because the narrative that we're leaving Afghanistan is self-defeating," Carter told an Army conference in Washington.

"We're not, we can't, and to do so would not be to take advantage of the success we've had to date."

Nato forces have been in Afghanistan since 2001.

Though the United States represents by far the largest contingent, Carter last week said several Nato defence ministers told him they were open to modifications to current plans.