“Iran’s expansion of its nuclear program, which was recently announced, will lead to further isolation and sanctions,” he wrote in his microblog on Twitter.

Pompeo called on the country to maintain the existing uranium enrichment standards in accordance with the Joint Comprehensive Action Plan (IPTF) on the Iranian nuclear program.

"The Iranian regime, having nuclear weapons, will pose an even greater threat to the world," said a spokesman for the US Department of State.

Earlier, France, Britain, Germany and Israel expressed concern over Iran’s decision to begin uranium enrichment above the 3.67% level envisaged by the UFID.

In Tehran, in turn, explained this step by the desire to keep the nuclear deal.