Washington (dpa) - US President Donald Trump on Monday said the US will impose "big sanctions" on Turkey, as he defended a withdrawal of US forces from northern Syria during the escalating conflict between Turkey and the Kurds.

Trump's announcement on Sunday of a withdrawal of around 1,000 troops from northern Syria and an earlier movement of troops away from Syria's border with Turkey - paving the way for a Turkish incursion - are being criticized across the political spectrum.

Critics accuse the president of abandoning the Kurds, a US ally, and setting the stage for a resurgence of the Islamic State extremist group, while also ceding influence to Russia and the government of Syrian President Bashar al-Assad.

In a series of tweets on Monday, Trump said "big sanctions are coming," as there appears to be bipartisan support among lawmakers for sanctions.

Turkey started its incursion into north-east Syria on Wednesday targeting the Kurdish-led Syrian Democratic Forces, which it believes are tied to the outlawed Kurdistan Workers' Party (PKK), a Kurdish insurgent group inside Turkey.

The incursion has been widely condemned by Turkey's Western allies amid fears of a severe humanitarian crisis.

It is unclear what sanctions will be agreed upon by lawmakers, and Trump has not announced any specific actions.

On Monday, Nancy Pelosi, speaker of the House of Representatives, said that there must be a bipartisan resolution overturning Trump's "dangerous decision in Syria immediately," in what would likely be a symbolic move.

She also said stronger sanctions are needed than what is being proposed to lawmakers by the White House.

"As we find ourselves in a situation where the President gave a green light to the Turks to bomb and effectively unleashed [Islamic State], we must have a stronger sanctions package than what the White House is suggesting," she said.

Republican Senator Lindsey Graham on Monday said the sanctions will be "crippling."

"We are gonna break his economy until he stops the bloodshed," Graham said, referring to Turkish Prime Minister Recep Tayyip Erdogan.

The US has been allied with Syrian Kurds since 2014 in the war against Islamic State, and together they worked to defeat the territorial caliphate and hold captive Islamic State fighters.

The Kurdish-led force said it has lost some 10,000 people in the war.