“Pray for our Kurdish allies who have been shamelessly abandoned by the Trump Administration,” Mr Graham, a close ally of the president in the US Senate, tweeted in a rare rebuke on Tuesday.
Mr Graham came out in swift opposition to the administration’s plan to remove US troops from northeast Syria, saying it would leave a vacuum that could allow the Islamic State to possibly restore its caliphate while also allowing Turkish troops to begin a massive assault on the Kurds, who the US have considered a strategic ally in its fight against terrorism.
His comments came as Turkish fighter jets began bombing the area of Syria in which the country had long planned to carry out a military offensive, with experts citing the abrupt US pullout for paving the way for the assault to take place.
A spokesperson for the SDF, a Kurdish-majority militia that also encompasses several smaller groups, described Mr Trump’s withdrawal as a “stab in the back”.
The militia has been the US' main ally in fighting Isis in Syria and has lost an estimated 11,000 fighters as it fought to take back strongholds from the militants earlier this year.
Mr Graham described the decision as a “disaster in the making” earlier this week and took to the president’s favourite TV network to air his concerns.
“I hope I’m making myself clear how short-sighted and irresponsible this decision is,” Mr Graham told Fox News. “I like President Trump. I’ve tried to help him. This, to me, is just unnerving to its core.”
Other Republicans and military officials have also expressed concerns the move will lead to potentially catastrophic consequences in the region.
Marco Rubio, a Florida Republican who ran against Mr Trump in the 2016 election, said his decision was “a grave mistake that will have implications far beyond Syria.”
Mitch McConnell, the Senate majority leader who has largely supported the president’s agenda on Capitol Hill, also slammed the decision in a statement.
“As we learned the hard way during the Obama Administration, American interests are best served by American leadership, not by retreat or withdrawal,” he said.
Susan Collins, a Maine Republican who has occasionally spoke out against the president, also called the move a “terribly unwise decision”.
Even Nikki Haley, Mr Trump’s former ambassador to the United Nations, called the move a “big mistake” on Twitter.
“The Kurds were instrumental in our successful fight against ISIS in Syria. Leaving them to die is a big mistake,” she wrote.
Mr Trump has shot down criticism of his decision in a series of tweets posted earlier this week, warning Turkey against attacking the Kurdish forces, which it views as terrorists.
“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,” he wrote. “The endless and ridiculous wars are ENDING! We will be focused on the big picture, knowing we can always go back & BLAST!”
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