U.S. President Donald Trump on Monday said the U.S. and Iran would continue talks on Thursday for a nuclear deal, adding that Tehran was a tough negotiator and that the main impediment to an agreement was over enrichment.

The president said any enrichment was unacceptable. “They don’t want to give up what they have to give up,” he said.

President Trump told reporters that Iran has given the administration its thoughts on a possible nuclear deal and is still seeking enrichment, which he said is not acceptable.