WASHINGTON, Sept. 7 (Xinhua) -- U.S. President Donald Trump said on Saturday that he had cancelled secret meetings with the Taliban leaders and Afghan president after a car bomb in Kabul killed one American soldier and 11 others on Thursday.

"Unbeknownst to almost everyone, the major Taliban leaders and, separately, the President of Afghanistan, were going to secretly meet with me at Camp David on Sunday," Trump said in one of a series of tweets on Saturday evening.

"They were coming to the United States tonight. Unfortunately, in order to build false leverage, they admitted to an attack in Kabul that killed one of our great great soldiers, and 11 other people. I immediately cancelled the meeting and called off peace negotiations," Trump added.

Referring to the Taliban which claimed responsibility for the attack, Trump said: "If they cannot agree to a ceasefire during these very important peace talks ... then they probably don't have the power to negotiate a meaningful agreement anyway."

Trump's tweets came as the United States and the Taliban were close to a deal, which is expected to end the over-18-year-old U.S. war in Afghanistan.

It was still unclear if Trump was calling a permanent halt to the peace negotiations.

Both the Taliban militants and the Afghan government forces have intensified operations in the war-torn country recently.