Afghanistan said yesterday the Taliban would have to be defeated on the battlefield after US President Donald Trump rejected the idea of talks with the militants following a series of deadly attacks.

The Taliban reacted to Trump's announcement by saying they never wanted to talk to the United States anyway, but one senior member of the group said he suspected efforts would still be made to get negotiations going.

Talking to reporters at the White House on Monday, Trump condemned the militant group for recent carnage in Kabul and said the United States was not prepared to talk now. He pledged to "finish what we have to finish".

His comments suggested he sees a military victory over the Taliban, an outcome that US military and diplomatic officials say cannot be achieved with the resources and manpower he has authorised.

A spokesman for Afghan President Ashraf Ghani said while the government had encouraged the Taliban to talk, the attacks in Kabul, including a suicide bomb attack on Saturday that killed more than 100 people, was a "red line".

"The Taliban have crossed a red line and lost the chance for peace," said the spokesman, Shah Hussain Murtazawi.

"We have to look for peace on the battlefield. They have to be marginalized."

He declined to comment directly on Trump's announcement.

A spokesman for the Taliban, who are fighting to oust foreign forces, defeat the US-backed government and impose their version of Islamic rule, said they never wanted to hold peace talks with the United States anyway.

"Their main strategy is to continue war and occupation," the spokesman, Zabihullah Mujahid, said in a statement.

He said Taliban fighters would respond in kind if the Americans wanted to focus on war: "If you emphasise war then our mujahideen will not welcome you with flowers."