The US House of Representatives has overwhelmingly passed a resolution against the decision to withdraw American troops from Syria, even as the US President Donald Trump argued that his actions had produced a “strategically brilliant” outcome.

A total of 129 members of Trump's Republican Party joined Democrats as the House denounced the withdrawal of US troops from northern Syria in a 354-60 vote.

Nancy Pelosi (centre), Sen. Chuck Schumer (right) and Steny Hoyer after meeting President Donald Trump at the White House. AP

The joint resolution called on Turkish President Recep Tayyip Erdogan to immediately halt military operations against Kurdish militants in Syria.

Trump said he had written to Erdogan to warn him about the consequences of invading Syria. But the letter was dated October 9 — the day Turkey launched the military operation.

Trump is facing an avalanche of criticism, the House on Wednesday voted 354-60 in favour of the measure, as 129 Republicans joined with all 225 Democrats in an unusually bipartisan demonstration of disapproval.

Turkish President Recep Tayyip Erdogan. File photo

In a sign of Trump's deteriorating relationship with Congress, where the House is conducting an impeachment inquiry, Democratic House Speaker Nancy Pelosi and Senate minority leader Charles Schumer walked out of what they said was an acrimonious White House meeting with Trump.

Schumer said Trump had called Pelosi a "third-rate politician" while the speaker said the president had experienced a "meltdown."

Trump then took to Twitter, accusing Pelosi of having her own "meltdown," while adding that the Democratic leader "needs help fast!"

"There is either something wrong with her 'upstairs,' or she just plain doesn't like our great Country," the president wrote.

'Not angels'

Faced with mounting bipartisan criticism in Washington over the abrupt pullout of US forces from Syria, Trump denied he had given Erdogan a "green light" to launch operations against the Kurds.

"President Erdogan's decision didn't surprise me because he's wanted to do that for a long time," Trump told reporters earlier in the day at the White House. "He's been building up troops on the border with Syria for a long time."

The US president disparaged the Kurdish allies he abandoned in the face of the Turkish offensive, saying they were "not angels," as well as his Republican critics at home.

"I didn't give him a green light," Trump said of a telephone conversation he held with Erdogan prior to the Turkish incursion. "Just the opposite of a green light.

Senate Majority Leader Mitch McConnell answers questions in Washington. AFP

"I wrote a letter right after that conversation, a very powerful letter," he said.

In the letter dated October 9, Trump told Erdogan "you don't want to be responsible for slaughtering thousands" of people and urged him not to be a "tough guy" or a "fool."

"History will look upon you favorably if you get this done the right and humane way," Trump wrote.

Trump emphasized to reporters that US troops were out of harm's way and that the fallout from the US withdrawal was for Syria, Turkey and Russia to work out among themselves.

"I view the situation on the Turkish border with Syria to be, for the United States, strategically brilliant," Trump said. "Our soldiers are out of there, our soldiers are totally safe. They've got to work it out.

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"Turkey has gone into Syria. If Turkey goes into Syria, that's between Turkey and Syria -- it's not between Turkey and the United States, like a lot of stupid people would like you to believe," he said.

In a late-night tweet Trump again defended his decision.

"I am the only person who can fight for the safety of our troops & bring them home from the ridiculous & costly Endless Wars, and be scorned. Democrats always liked that position, until I took it," he said.

As Trump tweeted, Vice President Mike Pence and Secretary of State Mike Pompeo were heading to Turkey to try to persuade Erdogan to halt the offensive.