(REUTERS) - Secretary of State Mike Pompeo is accelerating a plan to slash up to half of the United States embassy staff in Kabul.

It is a surprise move that some US officials say could undermine peace talks with Taleban militants, which so far have made only meagre progress.

Mr Pompeo's order comes about a year earlier than expected, sources told Reuters. The move was not accompanied by a justification.

One US official said the embassy drawdown should be seen as part of a broader strategy shift as the Trump administration moves from a focus on counter-terrorism to threats posed by Russia and China.

US officials have separately told Reuters that President Donald Trump plans to withdraw up to half of the 14,000 US troops now based in Afghanistan.

The Kabul embassy - America's largest diplomatic mission - currently boasts a workforce of about 1,500 and underwent a US$800 million (S$1 billion) expansion just a few years ago.

Analysts fear the reduction could erode an already strained relationship between Washington and Afghan President Ashraf Ghani.

In the meantime, fighting in Afghanistan has escalated in recent months, as both sides in the conflict seek to increase leverage in talks on a possible peace deal.