File photo:Xinhua

US President Donald Trump's decision to withdraw troops from northern Syria before an imminent Turkish incursion has drawn wide criticism by former officials, lawmakers from both parties as well as foreign policy pundits.

The White House said in a late Sunday statement that the US military "will not support or be involved in" an expected military operation by Turkey in northern Syria, and US forces "would no longer be in the immediate area."

Trump on Monday reaffirmed the pullout of US troops from northern Syria in a series of tweets. "We stayed and got deeper and deeper into battle with no aim in sight," he said, adding "it is time for us to get out of these ridiculous Endless Wars, many of them tribal, and bring our soldiers home."

A senior official of the Trump administration said on the same day that about 50 US military personnel stationed in the border area in northern Syria would be redeployed within Syria to some place where they are not in danger of being caught in the crossfire.

Trump's decision to redeploy US troops in northern Syria along with the Turkish offensive into the region put the fate of Syrian Kurdish fighters in uncertainty.

Ankara has long viewed the Syrian Kurdish militia as an extension of the Kurdistan Worker's Party, which is listed as a terrorist organization by Turkey.

Trump's tweets showed that he seemed unconcerned about the plight of the Syrian Kurdish fighters, a US ally in fighting the Islamic State (IS). He acknowledged that the Kurds fought with the United States, but also noted that the United States gave them "massive amounts of money and equipment."

Former officials of the Trump administration and lawmakers from both parties criticized Trump's decision to regroup US forces and abandon the Syrian Kurdish fighters as "impulsive" and "shortsighted", fearing it would lead to a resurgence of the IS and a humanitarian crisis for the Syrian Kurds following the Turkish incursion.

Senator Lindsey Graham, one of Trump's strongest Republican defenders in Congress, on Monday labeled Trump's move an "impulsive decision" that would unravel US gains and give IS terrorists breathing space.

Graham also tweeted that abandoning the Kurds was "the most dangerous signal possible," saying he would call for suspension of Turkey's NATO membership if it attacks Kurdish forces.

US House Speaker Nancy Pelosi, a Democrat, urged Trump to "reverse this dangerous decision" to withdraw, saying that the move sent a message to friends and foes alike that the United States is no longer a trusted partner.

Brett McGurk, the former presidential envoy for the global coalition to defeat the IS under both the Obama and the Trump administration, on his twitter slammed Trump's latest decision as being "impulsive" and with no knowledge or deliberation.

McGurk also questioned Turkey's ability to handle the captured IS fighters in the area, which the White House said on Sunday that Turkey would be responsible for after the US pullout.

"Turkey has neither the intent, desire, nor capacity to manage 60k detainees in al Hol camp, which (US Department of) State and DoD IGs (Inspector Generals of the Department of Defense) warn is the nucleus for a resurgent ISIS," he tweeted.

Facing extensive criticism at home, especially from Republicans, Trump seemed to recalibrate his tone on the Turkish operation in a later tweet on Monday. "If Turkey does anything that I, in my great and unmatched wisdom, consider to be off limits, I will totally destroy and obliterate the Economy of Turkey," said Trump, without offering details.

The Pentagon on Monday also cautioned Turkey in a later statement that its unilateral action creates risks for Turkey.

"We will work with our other NATO allies and Coalition partners to reiterate to Turkey the possible destabilizing consequences of potential actions to Turkey, the region, and beyond," the statement said.

Sinan Ulgen, a visiting scholar at Carnegie Europe in Brussels and a former Turkish diplomat, told Foreign Policy magazine that Trump was forced by Turkish President Recep Tayyip Erdogan to choose between Turkey and Syrian Kurds, and Trump has chosen the former.

"He does not see Syria as having any strategic value for the United States. He also did not want to risk totally alienating Turkey at a time when the containment policy towards Iran has reached a critical stage," Ulgen said.

Richard Haass, president of the Council on Foreign Relations, said that the latest decision would reinforce the already growing doubts about US reliability, jeopardize the Kurds who have been a valuable partner and create new space for terrorists.

"This decision fails on moral and strategic grounds," he noted.

(Matthew Rusling also contributed to the story)