The Biden administration “can’t wait forever for Iran to decide it wants to restart talks on returning to the 2015 nuclear deal that former President Donald Trump quit in 2018, the top US envoy for the negotiations said.

The US still hasn’t received any indication that Iran’s new president, Ebrahim Raisi, is prepared to commit to a seventh round of talks to come back into compliance with the accord known as the Joint Comprehensive Plan of Action, envoy Robert Malley said Friday in an interview with Bloomberg Television.

“We can’t wait forever as Iran continues its nuclear advances because at some point their advances will be such as to make a return to the JCPOA much less valuable to the US than it would otherwise be,” Malley said, although he added that the US was “prepared to be patient.”

“But let’s not drag this on for too long because some point, we’ll have to reach a different conclusion,” he said.

Six rounds of indirect talks in Vienna have so far been inconclusive, with Iran demanding that the US lift all sanctions that were imposed under the Trump administration as a condition for resuming compliance with the Iran deal. The US has said Iran needs to abandon its nuclear work as a condition to get sanctions relief.