US military chief General Joseph Dunford arrived in Afghanistan for a surprise visit on Monday for meetings with NATO and US officials.
Dunford, the chairman of the US joint chiefs of staff, "will have internal meetings on base" in the capital, Kabul, a spokesman for the NATO mission in Afghanistan said.
It was not clear whether he would also be meeting with Afghan officials during his visit, which is expected to last several days.
His arrival comes as the US considers sending more troops to Afghanistan, which has suffered a dramatic decline in security since the withdrawal of most international troops, as well as the end of their combat mission in December 2014.
US military sources estimate that some 11 per cent of the country is controlled by Islamist militants, while some 30 per cent is currently disputed.
Media reports have suggested that the US could send as many as 5,000 extra troops to Afghanistan, in addition to the 8,400 already there.
