Pelosi and other top Democrats say they walked out of the contentious White House briefing on Trump's decision to withdraw US troops from Syria after it devolved into an insult-fest and it became clear the president had no plan to deal with a potential revival of Isis in the Middle East.

The Senate Democratic leader, Chuck Schumer, told reporters Trump had called Pelosi a "third-rate politician". He said the meeting "was not a dialogue, this was sort of a diatribe, a nasty diatribe not focused on the facts".

Pelosi said: "I pray for the president all the time … I think now we have to pray for his health – this was a very serious meltdown on the part of the president."

She added Democrats "couldn't continue in the meeting because he was just not relating to the reality of it".