NEW YORK, USA (AP) — They may have his back on impeachment, but some of President Donald Trump’s most loyal allies are suddenly revolting against his decision to pull back US troops from northern Syria.

One chief Trump loyalist in Congress yesterday called the move “unnerving to the core”. An influential figure in conservative media condemned it as “a disaster”. And Trump’s former top NATO envoy said it was “a big mistake” that would threaten the lives of Kurdish fighters who had fought for years alongside American troops against the Islamic State group.

Trump’s surprise move, which came with no advance warning late Sunday and stunned many in his own Government, threatened to undermine what has been near lockstep support among Republicans at a critical moment in his presidency. Democrats are pursuing an impeachment inquiry in the House, while Republicans in the Senate stand as the president’s bulwark against being removed from office.

Senator Lindsey Graham, R-SC, who has been among Trump’s most vocal defenders, called the Syria decision “a disaster in the making” that would throw the region into chaos and embolden the Islamic State group.

“I hope I’m making myself clear how short-sighted and irresponsible this decision is,” Graham told Fox News. “I like President Trump. I’ve tried to help him. This, to me, is just unnerving to its core.”

Senator Marco Rubio, R-Florida, who has shrugged off the key allegation in the impeachment inquiry — that Trump pressured foreign powers to investigate a top Democratic rival — tweeted that Trump’s shift on Syria is “a grave mistake that will have implications far beyond Syria”.

Senator Susan Collins, R-Maine, who has been more willing than many Republicans to condemn Trump’s calls for foreign intervention in the 2020 election, called the Syria move “a terribly unwise decision”.

And Senate Majority Leader Mitch McConnell likened Trump’s latest foreign policy announcement to something from Barack Obama’s presidency.

“As we learned the hard way during the Obama Administration, American interests are best served by American leadership, not by retreat or withdrawal,” McConnell said.

Republicans in Congress have broken with Trump on Syria before. The GOP-controlled Senate voted overwhelmingly in February to oppose the withdrawal of US troops from Syria and Afghanistan the last time he unveiled a similar proposal without warning on Twitter late last year.

But the intensity, scope and timing of yesterday’s backlash makes this time different. In the face of a serious impeachment inquiry, Trump’s very political future depends on his ability to maintain the loyalty of his party on and off Capitol Hill.

“For Trump to make a very controversial move on Syria at the exact moment when he needs Senate Republicans more than ever is risky politics,” said former Trump aide Alex Conant, noting the significance for many Senate Republicans of the United States’ policy in northern Syria, where Kurds would be particularly vulnerable to a Turkish invasion.

“They’re not just going to send out a couple of tweets and move on,” Conant said.

For a day, at least, the intra-party clash dominated the political conversation, overshadowing the president’s near-constant campaign to undermine the Democrats’ impeachment investigation.

Nikki Haley, who was Trump’s hand-picked ambassador to the United Nations, cast the decision to withdraw US troops from northern Iraq as a betrayal of a key ally.

“The Kurds were instrumental in our successful fight against ISIS in Syria. Leaving them to die is a big mistake,” she wrote on Twitter.