The US Secretary of State has slashed aid to Afghanistan's government after a mission to Kabul failed to bridge a divide between feuding leaders as he moved forward with the Taliban on a deal to pull troops.

Mike Pompeo made the surprise trip in hopes of reviving a landmark US accord with the Taliban to end America's longest war and, stopping in Qatar on his way back, became the highest-ranking US official ever to meet the Islamist insurgents.

In stark criticism of a government backed for nearly two decades by the United States, Mr Pompeo voiced disappointment that President Ashraf Ghani and his rival Abdullah Abdullah could not bridge their differences when he met them in Kabul.

"Their failure has harmed US-Afghan relations and, sadly, dishonours those Afghan, Americans and coalition partners who have sacrificed their lives and treasure in the struggle to build a new future for this country," Mr Pompeo said in a statement.

Mr Pompeo said that the United States was immediately reducing $1 billion in aid and would pull another $1bn in 2021.

He said the United States would consider further cuts, including withdrawing support at any future donor conference.

Mr Pompeo also assured that the US would go ahead with its pull out of troops from Afghanistan, with a goal of removing all 13,000 by next year.

Officials said Mr Pompeo later met for an hour in Qatar's al-Udeid Air Base, which is also home to US forces, with three Taliban leaders including Mullah Baradar, a formerly imprisoned insurgent who has become their chief negotiator.

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US, Taliban sign troop withdrawal deal in Qatar

Mr Pompeo had flown to Doha for the 29 February signing of the accord with the Taliban but had not met then with the militant group, which has not given up its campaign of violence against the Afghan government or gone ahead with promised talks with Kabul.

But Mr Pompeo said that the Taliban had abided by its promise not to attack US forces and that the US would keep up its commitment.

"They committed to reducing violence and they've largely done that," Mr Pompeo told reporters on his plane.

On a US withdrawal, he said: "We're moving down that path as long as these violence levels remain beneath the threshold."