United States President Donald Trump on Monday said that US peace talks with the Taliban are over and announced that the US military has dramatically scaled up attacks on the insurgents in Afghanistan.

“They are dead. As far as I am concerned, they are dead,” Trump said at the White House about the long-running attempt to reach an agreement with the Taliban and extricate US troops from the country after 18 years of war.

Explainer: How Trump upended US-Taliban peace taks

The announcement followed Trump's dramatic cancelation of a secret plan to fly Taliban leaders in for direct talks at the Camp David presidential retreat over the weekend.

Driving another nail into the coffin of what had appeared to be nearly completed negotiations, Trump said that a US military onslaught on the guerrillas was now at its fiercest in a decade.

“Over the last four days, we have been hitting our enemy harder than at any time in the last ten years!” he said in a tweet.

On Sunday, Secretary of State Mike Pompeo said that “we've killed over a thousand Taliban in just the last 10 days.”

Trump angrily denied that the whiplash effect of his sudden shifts on Afghanistan was causing turmoil.

Until this weekend, there had been steadily mounting expectations of a deal that would see the US draw down troop levels in Afghanistan. In return, the Taliban would offer security guarantees to keep extremist groups out.

But then on Saturday, Trump revealed that he had canceled an unprecedented meeting between the Taliban and himself at storied Camp David, near Washington. He said this was in retaliation for the killing of a US soldier by the Taliban last week.

The cancelation — announced on Twitter — was the first time most Americans learned that such a dramatic meeting was even planned.

Many in Washington were shocked and some were angry that the Taliban had been on the point of visiting the presidential retreat on the eve of the anniversary of the September 11 terrorist attacks.

There was also widespread consternation at the characteristically unpredictable manner of Trump's negotiating style. But Trump denied any discord among government members including Vice President Mike Pence.

He accused journalists of trying “to create the look of turmoil in the White House, of which there is none.”

“A lot of Fake News is being reported that I overruled the VP and various advisers on a potential Camp David meeting with the Taliban. This Story is False! I always think it is good to meet and talk, but in this case I decided not to,” he tweeted.