KABUL (REUTERS) - Vice-President Mike Pence made an unannounced trip to Afghanistan to meet its leaders and underscore US commitment to the country, four months after President Donald Trump agreed to an open-ended war against insurgents here.

Pence arrived on a military plane at Bagram Airfield under the cover of darkness on Thursday night (Dec 21) leaving Washington on Wednesday.

He proceeded to fly via helicopter to Kabul, where he met President Ashraf Ghani and Chief Executive Abdullah Abdullah at the presidential palace.

Pence said he hoped his presence there was tangible evidence that the United States was "here to see this through".

In a reversal of his campaign call for a swift withdrawal of US forces from Afghanistan, Trump in August pledged a stepped-up military campaign against Taleban insurgents and signalled the United States would send more troops.

At the end of August, there were some 11,000 US troops in Afghanistan and more have since arrived.

Ghani expressed gratitude to the US government and said Afghanistan's partnership with the United States was cemented in sacrifice.