Senate Republicans are calling President Trump’s pullout of American troops from northern Syria a blunder that economic sanctions on Turkey will be useless to remedy.

The Trump administration and lawmakers from both parties are scrambling to slap Turkey with biting sanctions in a desperate bid to stop Ankara from annihilating the United States' Kurdish allies in Syria. But dismayed Senate Republicans are conceding that they expect sanctions to fail to deter Turkey from targeting the Kurds and said the damage to America’s reputation was already done.

“People are just grasping to come up with something,” said John Thune, the No. 2 ranking Senate Republican. “This was a mistake.”

Trump’s decision to remove American troops from northern Syria, where they had been deployed to combat the Islamic State, has exposed Kurdish fighters allied with the U.S. in that campaign to devastating attacks from Turkey. Recep Tayyip Erdoğan, president of Turkey, classifies the Kurds as enemies. To counter perceptions the U.S. abandoned an ally, Trump and Congress are threatening sanctions if Turkey continues its incursion into Syria against the Kurds.

The White House also has dispatched Vice President Mike Pence and Secretary of State Mike Pompeo to Ankara to pressure Erdogan.

Senate Republicans fear that Trump has ceded geopolitical influence in the Middle East to Russia and Iran, two troublesome American adversaries. “Sanctions aren’t going to do any good,” Utah Sen. Mitt Romney said. “Abandoning [the Kurds], in my opinion, was an enormous strategic mistake and represents one of the darkest days in American foreign policy history.”

Sen. Marco Rubio said sanctions, even if they do harm Turkey’s economy, could boost Erdoğan domestically. His authoritarian regime has been under pressure from a public that has grown unhappy with leadership. But defying the U.S. and waging war against the Kurds could revive his political standing.

Sanctions “aren’t going to change anything,” the Florida Republican said. “There is no way to unravel it, there is no way to undo some of the more significant damage it’s done.”

Top Democrats and Republicans in Congress, who have issued a rare bipartisan rebuke of Trump’s decision to pull troops from Syria and abandon the Kurds, were headed to the White House Wednesday afternoon to discuss the matter with the president. They are hoping to change his mind or convince him to adopt more aggressive action to influence Turkey, which is a member of the North Atlantic Treaty Organization.

But they could find Trump stubbornly satisfied with his position. “I view the situation on the Turkish border to be, for the United States, strategically brilliant,” the president told reporters Wednesday. “It’s not our problem."

Republican hawks are periodically critical of Trump’s foreign policy. In this instance, however, a broad cross section of congressional Republicans has condemned the president. In the Senate, Republicans that typically shy away from publicly scolding Trump, even when they disagree, are speaking out. Chief among them is Majority Leader Mitch McConnell of Kentucky, who is up for reelection this year.

“I’m sorry that we are where we are,” McConnell said. “I hope that the vice president and the secretary of state can somehow repair the damage.”