US Secretary of State Antony Blinken told NBC News Wednesday in Brussels he is “not overly optimistic about actually getting an agreement,” in Iran nuclear talks.

Blinken added he believes “it would be in the best interests of our country if we can get back into compliance” with the 2015 Iran nuclear deal “if Iran will do the same.”

Efforts to revive the agreement, which former president Donald Trump abandoned in 2018 prompting Iran to expand its nuclear program, are currently paused. Talks in Vienna have struggled to agree which US sanctions, vastly extended by Trump, violated the agreement and exactly how Iran’s nuclear program, expanded since 2019, should be returned to the limits of the deal, the JCPOA (Joint Comprehensive Plan of Action).

Blinken stressed Washington’s cooperation with France, Germany, and the United Kingdom, without mentioning China and Russia, also JCPOA signatories and part of the Vienna process.

Asked if Iran’s Revolutionary Guards were a “terrorist organization,” Blinken replied “they are,” but then added he was “not going to get into the details of where we are in the negotiations.” One point reportedly at issue in the Vienna talks is whether the IRGC should be removed from the US list of ‘foreign terrorist organizations,’ where they were placed by Trump in 2019 after introducing ‘maximum pressure’ sanctions. The IRGC are the only example of any state’s armed forces designated in this way and are subject to other US sanctions.