US President Donald Trump has promised to work with both parties in Congress to hit Turkey with “powerful sanctions,” after Ankara’s military launched a much-criticized operation against Kurdish militias in northern Syria.

“Dealing with @LindseyGrahamSC  and many members of Congress, including Democrats, about imposing powerful Sanctions on Turkey,” Trump tweeted on Sunday. “Treasury is ready to go, additional legislation may be sought. There is great consensus on this. Turkey has asked that it not be done. Stay tuned!”

Trump’s announcement comes as Turkey continues a military offensive against Kurdish militia groups in northern Syria, whom it considers terrorists. The offensive was launched following Trump’s withdrawal of US forces from the area, where they had fought alongside the Kurds against Islamic State (IS, formerly ISIS).

Accused of “abandoning” the Kurds, Trump has repeatedly stressed his desire not to get involved in another “endless war” in the Middle East. He has, however, faced pressure from lawmakers on both sides of the aisle to punish Turkey for its anti-Kurdish operation.

South Carolina Republican Senator Lindsey Graham, mentioned in Trump’s tweet, has long been a proponent of keeping US boots on the ground in Syria, and urged Trump on Friday to “change course” and use the US military to block the Turkish offensive. Graham and Democrat Senator Chris Van Hollen (Maryland) have also unveiled a sanctions bill that would personally target Turkish President Recep Tayyip Erdogan and his top officials, and freeze military aid to Ankara.

For the moment, sanctions seem to be the Trump administration’s favored route. Treasury Secretary Steven Mnuchin said on Friday that by deploying “powerful sanctions,” the US can “shut down the Turkish economy if we need to.”

Aside from the potential targeting of civilians – which Erdogan has vowed to avoid – the US is concerned that Islamic State prisoners held in Kurdish-controlled regions may escape amid the conflict. Kurdish officials said earlier on Sunday that “hundreds” of Islamic State-linked prisoners had already escaped from a camp hit by Turkish shelling.