Donald Trump has declared talks between the US and the Taliban “dead” after he called off a Camp David meeting over the weekend, triggering fears of a spike in violence in Afghanistan in the run-up to presidential elections due later this month.

Trump announced on Sunday that he had cancelled secret Camp David meetings with the Afghan president, Ashraf Ghani, and Taliban leaders, following a car bomb attack in Kabul on Thursday. And he said negotiations with the Taliban, which appeared to have been close to a deal, were at an end.

“They’re dead so far as I’m concerned,” Trump told reporters on the South Lawn of the White House. “They thought that to kill people in order to put themselves in a little better negotiating position when they did that they killed 12 people … And you can’t do that can’t do that with me. So they’re dead as far as I’m concerned. And we’ve hit the Taliban harder at the last four days than they’ve been in over 10 years.”

Trump’s tweeted announcement on Saturday came as a shock in Washington and Kabul, where there was disbelief that the president would have invited the Taliban to an iconic presidential venue in the same week as the anniversary of the 9/11 attacks.

There was also scepticism that the bombing of Thursday in Kabul was the real reason the talks were called off.

The Taliban issued a statement saying an agreement had been “finalised” and that talks had ended in “a good atmosphere” but the deal had been sabotaged by Trump.

Taliban warns of more US dead after Trump says he cancelled peace talks Read more

“Reacting to just one attack, just before the signing of the agreement, shows neither patience nor experience,” the statement said.

The Taliban would continue their “jihad” against foreign “occupation”, the statement said. “Now, the announcement by the president of the United States, Donald Trump, of an end to negotiations with the Islamic Emirate [the Taliban] will harm America more than anyone else; it will harm its credibility, and further expose its anti-peace stance to the world; it would [result in] an increase in financial damage and casualties to its forces.”

The Taliban are expected to step up attacks on preparations for presidential elections on 28 September.

President Ghani had been opposed to the US-Taliban deal negotiated in Qatar by the US special envoy, Zalmay Khalilzad, because the Afghan government had been excluded from the talks, and the agreement reportedly gave no guarantees on the holding of this month’s election or the survival of the Kabul government. Nor did it commit the Taliban to talking directly to Ghani or his ministers.

According to most accounts, the agreement was extremely limited, exchanging the offer of a US troop withdrawal for a Taliban undertaking that attacks on the US would not be launched from Afghanistan.

“To satisfy his own ego and narrow political interests, Trump was willing to host the Taliban at Camp David and force [the] Afghanistan government to agree to a deal that benefited the Taliban only,” Vali Nasr, a former US special adviser on Afghanistan and Pakistan, said on Twitter. “And he couldn’t even pull that off.”

Mike Pompeo, the US secretary of state, said that Khalilzad had been recalled from Qatar and that it was up to the Taliban when talks would resume.

“The president ultimately made the conclusion that the meetings today wouldn’t deliver on the outcome that he is demanding we get for the American people,” Pompeo told CBS News on Sunday. “And when he saw that, when he saw that they couldn’t deliver on the reduction in violence commitments that they had made, he said there’s no sense in having this meeting.”

According to Time, Pompeo had refused to sign the “agreement in principle” Khalilzad had said he reached in Doha after nearly a year of talks because of his doubts about the deal and because the Taliban wanted to sign the agreement as the “Islamic Emirate of Taliban”, a recognition the secretary of state was not ready to bestow.

Facebook Twitter Pinterest The Afghanistan president, Ashraf Ghani, addresses Afghan security forces in Kabul on Monday. He was excluded from and opposed to the US-Taliban deal. Photograph: Omar Sobhani/Reuters

It was also reported that the US national security adviser, John Bolton, and the vice-president, Mike Pence, opposed meeting Taliban representatives in Camp David, a few days before the 18th anniversary of the 9/11 attacks. Trump declared such reports “Fake News” but did not directly contradict them, saying only: “I always think it is good to meet and talk, but in this case I decided not to.”

Former officials and Afghan experts doubted that Thursday’s attack in Kabul – in which 10 civilians, one US soldier and one Romanian soldier were killed – was the real reason for the cancellation. They pointed out that the Taliban had kept up attacks throughout a year of negotiations, and that US has also fought and negotiated at the same time.

Experts were also sceptical that Taliban leaders had been ever intended to fly to Camp David on Sunday.

According to one source familiar with the talks: “Both sides had initialled the agreement, but… Trump wanted to stage something at Camp David. He wanted to be the guy who did the deal. He wanted a TV show.”

According to this account, the Taliban were concerned how they would be treated once arriving in the US. So to pre-empt reports that Trump had been spurned, the president sought to “control the narrative” by tweeting he had cancelled a Camp David meeting that was never going to occur.

“What looks to be the failure of these particular talks makes a negotiated end to the war, for now, less likely,” wrote Kate Clark of the Afghanistan Analysts Network.