(JNS) U.S. Special Envoy for Iran Robert Malley said this week that given the pace of Iran’s nuclear program, there are only “some weeks left, but not much more” to revive the 2015 Joint Comprehensive Plan of Action (JCPOA).

“At some point in the not-so-distant future, we will have to conclude that the JCPOA is no more, and we’d have to negotiate a wholly different deal, and of course we’d go through a period of escalating crisis,” Malley told CNN.

The seventh round of negotiations between Iran and the other signatories to the JCPOA began on November 29. Progress has reportedly stalled as Iran has made demands for more concessions.

“It seems very clear [Iran] is trying to build leverage by expanding their nuclear program and hoping to use that leverage to get a better deal. It won’t work,” said Malley. “We’re prepared to go back to the JCPOA as it was negotiated in 2015 and 2016, neither more nor less.”

U.S. National Security Adviser Jake Sullivan is in Israel this week for talks in Jerusalem to discuss the state of Iran’s nuclear program. Sullivan said on Friday that the Iran negotiations “are not going well.”

Israel has called for a tougher stance against the Islamic Republic and reportedly worries that an agreement with Iran will lead to sanctions relief without a significant rollback of Tehran’s nuclear program.