Negotiations between Iran and the U.S. on reviving the 2015 nuclear deal are close to completion, the European Union’s senior negotiator at the talks said Sunday evening, but it remained unclear whether Tehran will accept the final deal.

The text of an agreement could be closed in coming hours, said the EU’s Enrique Mora, the coordinator of the talks. However, Iran must still decide whether to set aside its demand that the nuclear deal can only be revived if a multiyear United Nations atomic agency probe into its nuclear program is closed…

However, Iran came into last week’s talks insisting that the U.N. atomic agency’s three-year probe into undeclared nuclear material found in the country must be closed down if the nuclear deal is revived. Several Western diplomats said Sunday that Tehran has doubled down on this condition in the past few days of talks and there is no agreement on the issue.

The probe into the man-made nuclear material found in Iran is highly sensitive for Tehran, which has always claimed it has never sought nuclear weapons. Iran has stonewalled the investigation and given answers that the agency has said aren’t credible.

However, Western officials have said Iran needs to cooperate with the International Atomic Energy Agency and insisted they wouldn’t intervene to close the probe or to set a fixed deadline for the agency’s work.