The United States said on Wednesday it will terminate sanctions waivers that had allowed Russian, Chinese and European companies to carry out work originally designed to make it harder for Iranian nuclear sites to be used for weapons development, Reuters reported.
The waivers, which officials said expire on 27 July, covered the conversion of Iran's Arak heavy water research reactor, the provision of enriched uranium for its Tehran Research Reactor and the transfer of spent and scrap reactor fuel abroad.
In a statement, US Secretary of State Mike Pompeo gave no precise justification for the move, which will halt some work originally designed to make it more difficult for Iran to potentially develop fissile material for nuclear bombs.
However, Pompeo said Washington would extend for 90 days a waiver allowing foreign work at a Russian-built nuclear power plant at Bushehr to ensure safety.
The wider decision seemed aimed at tightening the US "maximum pressure" policy applied since Washington abandoned the 2015 Iran nuclear deal two years ago. That deal eased economic sanctions on Iran in return for curbs on its nuclear program.
"Because of our pressure, Iran's leaders are facing a decision: either negotiate with us or manage economic collapse," US Special Representative for Iran Brian Hook told reporters.