Washington: US President Donald Trump has cancelled a secret meeting at Camp David with Taliban leaders and the president of Afghanistan and had called off long-running negotiations with the Afghan insurgent group that appeared to be nearing a peace agreement.

"Unbeknownst to almost everyone," Trump wrote in a series of tweets, Taliban leaders and the Afghan president, Ashraf Ghani, were headed to the US on the weekend for what would have been a historic meeting at Camp David on Sunday

But Trump angrily said that "in order to build false leverage," the Taliban had admitted to a suicide car bomb attack on Thursday that had killed a US soldier and 11 others in Kabul, the Afghan capital. "I immediately cancelled the meeting and called off peace negotiations," he wrote.

"If they cannot agree to a ceasefire during these very important peace talks, and would even kill 12 innocent people, then they probably don't have the power to negotiate a meaningful agreement anyway," Trump wrote. "How many more decades are they willing to fight?"