“If Iran takes any further enrichment-related steps, the international community will have to consider additional measures to restrain Iran’s nuclear ambitions,” State Department spokesman Sean McCormack said.
The United States suspects research and development work that Tehran said would restart on January 9 could help what Washington believes is its pursuit of a nuclear bomb, he told reporters.
Iran denies seeking nuclear weapons.
The United States has been pressing for months for Iran to be referred to the United Nations Security Council for possible sanctions because it says Iran has failed to dispel suspicions it is building a nuclear bomb.
International resistance to such a move has gradually been eroding as Iran has taken an increasingly hard line insisting on its right to develop peaceful nuclear programs to generate power.
Earlier on Tuesday, Iran said it would resume nuclear research and development which it suspended two years ago to defuse international pressure over its atomic ambitions.
Such work may include the manufacture and assembly of centrifuges used for uranium enrichment, the most sensitive part of the nuclear fuel cycle. It could also include some small-scale enrichment tests.
Diplomats said Tuesday’s move, which follows Iran’s resumption of uranium conversion in August, was a serious blow to diplomatic efforts to resolve the dispute.
