After weeks of tense negotiations aimed at preventing Iran from obtaining a nuclear weapon, the Trump administration has offered a concession that may open a path to a compromise.

Over the weekend, the United States proposed the outline of a deal that would seem to allow Iran to temporarily continue enriching uranium. That has been a sticking point in the talks, which have been at an impasse.

On Wednesday, in his first public remarks since the proposal was reported on, Iran’s supreme leader, Ayatollah Ali Khamenei said that it would be “useless” for Iran to build nuclear power plants without being able to enrich uranium over the long term, framing the U.S. proposal as an attempt to obstruct Iran’s nuclear industry and self-reliance.

It was not immediately clear whether his statements were part of the rhetorical theater of negotiations, or an actual position from the government. Notably, he did not order a halt to the negotiations with the United States, though he also did not say whether they would continue.