A US official says the stalemate in the Vienna talks over the terrorist designation of Iran’s Revolutionary Guard is so sensitive that a compromise seems impossible and unrealistic.

The official familiar with the issue told Politico on Thursday that Washington is unwilling to include the removal of the IRGC from the US list of terrorist organizations since it falls beyond the contours of the original 2015 nuclear deal -- formally known as the Joint Comprehensive Plan of Action, or JCPOA.

“The US position has been that unless Iran agrees to take certain steps to assuage security concerns beyond the JCPOA, Washington will not lift the terror designation, which itself is beyond the JCPOA,” the unnamed source said.

He added that “the Biden administration is highly unlikely at this point to drop the designation in the context of the JCPOA talks” especially now that the administration is facing bipartisan political resistance at home and “given ongoing threats by the IRGC against [Americans]”.

The agreement that seemed imminent only two months ago hit a few hurdles along the way. First the Islamic Republic demanded that all sanctions – including over its missile and drone programs as well as human rights– be removed, then Russia - an original signatory of the JCPOA — demanded sanctions protections for any future business with Iran following its invasion of Ukraine. However, dropping the terrorist label of the IRGC seems like the tallest hurdle that has run the talks aground.