US Secretary of State Mike Pompeo pressed European nations to stop Iran's "extortion" after Tehran again reduced its commitments under a nuclear deal in response to US sanctions.
"We are confident that the UK, France and Germany - indeed, all civilized nations - will take decisive actions to stop Iran's nuclear extortion," Mr Pompeo wrote on Twitter.
We are confident that the UK, France, and Germany - indeed, all civilized nations - will take decisive actions to stop Iran's nuclear extortion.
— Secretary Pompeo (@SecPompeo) September 6, 2019
Iran has been negotiating with European powers that hope to salvage the 2015 nuclear accord despite the withdrawal last year by the United States, which reimposed punishing sanctions.
Iranian President Hassan Rouhani said on Wednesday that Tehran would step up its research and development work.
The head of the country's atomic energy organisation is due to hold a press conference on Saturday.
Iran said it would fully adhere to the deal if it sees economic relief, such as a greater ability to sell its oil, currently banned under unilateral US sanctions, or a credit line mulled by France.
Iran is hoping to air its frustrations by taking 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.
Mr Pompeo accused Iran, which said the new research and development would focus on centrifuges, of seeking to build "their nuclear weapons systems."
"Those things are unacceptable," Mr Pompeo said in a radio interview given while visiting his home state of Kansas.
Despite his administration's hawkish stance, US 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.
