US Defense Secretary Jim Mattis landed in Kabul on Friday for an unannounced visit to war-torn Afghanistan, adding his weight to a flurry of diplomatic efforts to bring the Taliban to the negotiating table.

His trip comes a little more than a year after President Donald Trump unveiled a revamped strategy for Afghanistan that saw him commit thousands of additional US forces to the country on an open-ended basis. His arrival in Kabul comes at a sensitive time in the 17-year war.

The grinding conflict has seen little progress by Afghan or US forces against the Taliban, the country's largest militant group. 

Afghan and international players have been ratcheting up efforts to hold peace talks with the Taliban, which was toppled from power by US-led forces in 2001.

An unprecedented ceasefire in June followed by talks between US officials and Taliban representatives in Qatar in July fuelled hopes that negotiations could bring an end to the fighting.

But a recent spate of attacks by the Taliban and the smaller but potent ISIL group that left hundreds of people dead has severely dented that optimism.