US Secretary of State Mike Pompeo said Iran's moves to increase its level of uranium enrichment and stop inspections by a UN watchdog were an attempt at "nuclear extortion" that the world should reject.
Iran's hardliner-dominated parliament approved a bill on December 1 that would require the government to boost its uranium enrichment to 20 per cent if European signatories to the 2015 nuclear deal do not provide relief from oil and banking sanctions imposed by the United States.
It also called for an end to nuclear inspections of its nuclear facilities by the International Atomic Energy Agency.
The bill was endorsed by Iran's Guardian Council but has yet to be approved by President Hassan Rouhani, who suggested the US could change its policy when president-elect Joe Biden assumes office in January.
"The United States condemns the law recently approved by Iran's Majlis and Guardian Council, which is nothing more than the regime's latest ploy to use its nuclear programme to try to intimidate the international community," Mr Pompeo said on Friday.
The caps on enrichment and IAEA inspections are part of the nuclear deal, formally known as the Joint Comprehensive Plan of Action, aimed at preventing Iran from developing atomic weapons.
US President Donald Trump pulled out of the agreement in 2018, citing Iran's continued development of ballistic missiles and destabilising activities in the Middle East, and imposed sanctions that have throttled the Iranian economy and led to a series of escalations by both sides.
Mr Pompeo pointed out that Iran was already exceeding the limits on enrichment levels as well as expanding its uranium stockpile and researching, producing, and installing advanced centrifuges, and had "for nearly two years stonewalled IAEA efforts to resolve questions about possible undeclared nuclear materials and activities".
"A reduction in Iran’s co-operation with the IAEA or enrichment to the 20 per cent level would constitute a serious escalation that moves Iran closer to the ability to obtain a nuclear weapon," he said.
"The international community must not reward the regime’s dangerous gamesmanship with economic appeasement.
"If the Iranian regime seeks sanctions relief and economic opportunity, then it must first demonstrate that it is serious about fundamentally changing its behaviour by ceasing its nuclear extortion and negotiating a comprehensive deal that addresses its development of ballistic missiles and its support for terrorism, unjust detention, and other destabilising activities in the region."