President Donald Trump announced Sunday that he had canceled a secret meeting with major Taliban leaders at Camp David.

“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 wrote on Twitter.

Trump said that Taliban leaders admitted responsibility for an attack in Kabul that killed a U.S. service member, a Romanian service member, and ten civilians near the United States embassy in Kabul.

He said that the Taliban was trying to “build false leverage” in the ongoing peace talks.

“I immediately cancelled the meeting and called off peace negotiations,” he wrote. “What kind of people would kill so many in order to seemingly strengthen their bargaining position? They didn’t, they only made it worse!”

Trump said that if the Taliban could not agree to a ceasefire, it was unlikely that they could negotiate peace.

“How many more decades are they willing to fight?” he asked.

Trump has vowed to end the war in Afghanistan, but conclusive peace talks between the Taliban and the Afghanistan government remain elusive.

“We’ve been a peacekeeper there, in a way, for 19 years and at a certain point, you have to say, ‘That’s long enough,’” Trump said in August.