In its Monday response to a draft nuclear deal agreement proposed by the European Union -- which the EU has described as a "final" draft - Iran did not demand that the Iranian Revolutionary Guard Corps be removed from the State Department's list of Foreign Terrorist Organizations, the official said.

"The current version of the text, and what they are demanding, drops it," the official said, noting that the US had repeatedly and consistently rejected the demand. "So if we are closer to a deal, that's why."

The Iranians also dropped demands related to delisting several companies tied to the IRGC, the official said.

The official added that "the President has been firm and consistent that he will not lift the terrorism designation of Iran's Revolutionary Guards Corps." But the official said that while a deal is now "closer than it was two weeks ago, the outcome remains uncertain as some gaps remain. President Biden will only approve a deal that meets our national security interests."

Progress from this point forward could be slow, another senior administration official said. But there does seem to be more momentum now than there has been in the past year.