Rubio said in a podcast interview released Wednesday that Iran could import enriched material for a peaceful program.

A second round of nuclear talks between the United States and Iran concluded on Saturday, with both sides indicating progress. Delegations from both countries met in Rome for negotiations following an initial round in Oman last weekend.

Iran is ringing two deeply buried tunnel complexes with a massive security perimeter linked to its main nuclear complex, a report said Wednesday, amid U.S. and Israeli threats of attack.