Taliban vows to fight on after Trump says talks are 'dead'

US president said he is escalating the fight against the insurgents after cancelling secret talks that were scheduled to be held at Camp David

President Donald Trump speaks with reporters as he walks to Marine One on the South Lawn of the White House, in Washington. AP

The Taliban vowed to carry on fighting against American forces and the Afghan government after US President Donald Trump said that talks with the militants were "dead", raising the prospect of heightened violence in the country wracked by 18 years of war.

"We had two ways to end occupation in Afghanistan, one was fighting, the other was talks and negotiations," Taliban spokesman Zabihullah Mujahid told AFP.

"If Trump wants to stop talks, we will take the first way and they will soon regret it."

The American leader said on Monday that he is escalating the war with the extremist group again after cancelling secret talks with the insurgents.

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

The announcement came after Trump's cancellation of a top-secret plan to fly Taliban leaders in for direct talks at Camp David, the presidential retreat outside Washington.

Driving another nail into the coffin of what had appeared to be nearly finalised negotiations, Trump said that a US military onslaught on the insurgents was back to 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 wrote in a tweet.

US Secretary of State Mike Pompeo said that "we've killed over a thousand Taliban in just the last 10 days".

He was staunch in his defence of the president's moves. "When the Taliban tried to gain negotiating advantage by conducting terror attacks inside of the country, President Trump made the right decision to say that's not going to work," he said.

In the face of widespread criticism about his negotiating tactics and changing positions, Mr Trump said that "in terms of advisers, I took my own advice".

But Mr Trump denied any discord among government members including Vice President Mike Pence.

In a tweet, he accused journalists of trying "to create the look of turmoil in the White House, of which there is none".

Getting out of Afghanistan, where US troops have fought a largely fruitless battle against the Taliban over nearly two decades, was a top priority.

It is widely thought that Trump has been pushing for a withdrawal of US troops in time for his 2020 reelection bid.

Mr Trump repeated on Monday that he wanted "to get out by the earliest possible time".

However, whether because of last week's killing of a US soldier, as he says, or due to wider misgivings, that goal now appears in tatters.

"They did a mistake," Mr Trump said of the Taliban's deadly bomb attack.

Several Republican politicians concurred with the president's decision on the talks.

"I've never believed that a deal with the Taliban is either easy or imminent," Senator Marco Rubio said.

Senator Mitt Romney said that "it wouldn't have been my choice to have the Taliban at Camp David" - an opinion echoed by Senator Ron Johnson, who said he was "glad" the talks were not held there.

"I don't see where those negotiations go. At some point in time if you want peace you have to talk to them, I don't deny that," said Johnson.

"But right now they're murdering too many people."

Zalmay Khalilzad, the lead US negotiator, recently announced that he had reached an agreement in principle with the Taliban. Under the deal, the US would withdraw about 5,000 US troops within 135 days of signing. In exchange, the insurgents agreed to reduce violence and prevent Afghanistan from being used as a launch pad for global terror attacks, including from a local ISIS affiliate and Al Qaeda.

Mr Pompeo said the Taliban agreed to break with Al Qaeda – something that past administrations have failed to get the Taliban to do.

The insurgent group hosted Al Qaeda leader Osama bin Laden as he masterminded the 9/11 attacks in 2001. After the attacks, the US ousted the Taliban, which had ruled Afghanistan with a harsh version of ultra-conservative Islamic law from 1996 to 2000.