Iran has been negotiating with European powers that hope to salvage the accord despite US sanctions

US Secretary of State Mike Pompeo said Friday that Iran's latest reduction in commitments to a nuclear deal -- made in retaliation for US sanctions -- was "unacceptable."

"They announced... that they're going to continue to do more research and development on their nuclear weapon systems. Those things are unacceptable," Mr Pompeo told Kansas City radio station KCMO.

Iranian President Hassan Rouhani made the announcement Wednesday and the country's atomic energy organization is set to hold a press conference on Saturday, as Tehran shows its frustration with the 2015 deal.

Iran has been negotiating with European powers that hope to salvage the accord despite the reimposition of sanctions by the United States, which last year pulled out of the deal.

Despite his hawkish stance, President Donald Trump has said he is willing to speak with Iran, a prospect proposed by France.

"For months now President Trump has said that he'd be happy to meet with Iranian leadership with no preconditions. But our outcome from those conversations is also unambiguous," Mr Pompeo said.

In addition to ending the nuclear steps, Mr Pompeo said the United States wanted Iran to end its "terror campaigns" through proxy groups and its development of missiles.

Iran has already taken a series of small but symbolic steps to reduce compliance with the 2015 deal, in which it sharply curtailed its nuclear work in return for promises of sanctions relief.