Afghan forces have improved their performance over last year, a time when they saw a series of setbacks in their struggle against the Taliban, a United States general said Wednesday.

"We are cautiously optimistic about the coming months because overall we do believe that they have some momentum right now," senior spokesman for US forces in Afghanistan Charles Cleveland said via videoconference from Kabul.

"We do believe that the ANDSF has performed better this year than they were performing last year," he said, using the acronym for the Afghan national troops.

Last year concerns that Afghan forces lacked the ability to resist the Taliban led the United States to postpone indefinite withdrawal of its own troops.

The administration of President Barack Obama is under pressure to reevaluate the number of US soldiers that will stay in Afghanistan in 2017, now fixed at 5,500.

Cleveland said Afghan forces are progressing because they are now in "an offensive mindset" -- sometimes taking their own initiative in attacking the Taliban.

"They are getting better in employing their newer capabilities," including use of US-provided A-29 aircraft, MD-530 helicopters and intelligence, surveillance and reconnaissance tools.

Cleveland added that their special operations capability is "doing exceptionally well."

General John Nicholson, the new top commander of American and NATO troops in Afghanistan, is expected to conclude his assessment of troop needs for 2017 soon.

Cleveland expects him to brief his military chain of command "in the next couple of days."