"We anticipate there's an announcement coming" that Lieutenant General Scott Miller has been nominated for the role, the official said.

Miller, 57, has for two years headed up the secretive Joint Special Operations Command (JSOC) and has lengthy experience working with some of America's most elite fighters.

If confirmed by the Senate, Miller would take over from General John Nicholson, who is rotating out of his post after a two-year deployment.

According to the Wall Street Journal, which first reported Miller's selection, he was a captain overseeing a group of Delta Force commandos in the Battle of Mogadishu in 1993.

That incident was made famous by the book and movie "Black Hawk Down."

Miller's deployment to Afghanistan, which would see him promoted to four-star general, comes at a time when local security forces are still struggling to contain a resurgent Taliban and the Islamic State jihadist group has conducted several high-profile suicide attacks.

Currently, there are about 14,000 US troops in Afghanistan, providing the main component of the NATO mission there to support and train local forces.

Some of the US forces are involved in counterterrorism operations, particularly against the local IS group.

In a statement, the Pentagon said: "We have nothing to announce at this time. We do not discuss internal deliberations."