WASHINGTON, May 4. /TASS/. The United States may impose sanctions on the countries providing assistance to expand Iran’s Bushehr Nuclear Power Plant beyond the existing reactor unit, US State Department Spokesperson Morgan Ortagus said in a statement.

Earlier, US Secretary of State Mike Pompeo tightened restrictions against Iran’s nuclear program.

"Starting May 4, assistance to expand Iran’s Bushehr Nuclear Power Plant beyond the existing reactor unit could be sanctionable. In addition, activities to transfer enriched uranium out of Iran in exchange for natural uranium could be sanctionable," Ortagus noted.

The US will end waivers from its sanctions, which enable Tehran to exchange enriched uranium into the so-called yellow cake, a concentrate obtained from processing uranium ore.

The Bushehr NPP was built by Russia. Moscow and Tehran have agreed on constructing the second and third energy units. In November 2018, after Washington had restored its unilateral restrictive measures against Iran’s energy sector, the State Department admitted that this cooperation could be targeted by US punitive steps.

According to Ortagus, the Iranian authorities "must stop all proliferation-sensitive activities, including uranium enrichment." "We will not accept actions that support the continuation of such enrichment. We will also no longer permit the storage for Iran of heavy water it has produced in excess of current limits; any such heavy water must no longer be available to Iran in any fashion."

The diplomat also stressed that Pompeo "took steps to permit the continuation of projects that help restrict Iran’s ability to reconstitute its past nuclear weapons program." The US policy "preserves oversight of Iran’s civil nuclear program, reduces proliferation risks, constrains Iran’s ability to shorten its "breakout time" to a nuclear weapon, and prevents the regime from reconstituting sites for proliferation-sensitive purposes."

"We reserve the right to revoke or modify our policy covering these nonproliferation activities at any time if Iran violates its nuclear obligations or commitments or we conclude that such projects no longer provide value in constraining Iranian nuclear activities," she explained.

Pompeo believes that Tehran must declare to the International Atomic Energy Agency (IAEA) a full account of the prior military dimensions of its nuclear program, and verifiably abandon such work in perpetuity. "Additionally, he reiterates his call that Iran must stop enrichment and never pursue plutonium reprocessing."

The US keeps waivers from sanctions concerning Bushehr, as well as nuclear facilities in Arak and Fordow, but cuts their period from 180 to 90 days.

"The Trump administration continues to hold the Iranian regime accountable for activities that threaten the region’s stability and harm the Iranian people," Ortagus said. "The United States will continue to impose maximum pressure on the Iranian regime, and remains committed to denying Iran any pathway to a nuclear weapon."

Washington reinstated sanctions against Iran, including a ban on oil purchase, in November 2018 shortly after US President Donald Trump had made a decision on the US unilateral withdrawal from the Joint Comprehensive Plan of Action (JCPOA). The 2015 Iran nuclear deal, signed between Iran and six world powers (Russia, China, the UK, the US Germany and France) limited Tehran’s nuclear activities in exchange for lifting UN Security Council’s sanctions and unilateral restrictions of the US and the EU.

However, other participants of the deal did not back the US move and remained committed to the Iran nuclear deal. In its turn, the IAEA highlights in its report that Iran observes its commitments under the agreement and its activity is subject to thorough checks.