US Secretary of State Mike Pompeo will leave Washington on Thursday to travel to Doha to take part in the start of long-delayed intra-Afghan peace talks, President Donald Trump said.

"Secretary of State Mike Pompeo will be departing this evening on a historic trip to Doha ... for the beginning of intra-Afghan peace negotiations," he said

"I urge the negotiators to demonstrate the pragmatism, restraint, and flexibility this process will require to succeed," Pompeo earlier said in a statement on Thursday.