Beirut/Vienna (Reuters): Iran ordered its nuclear scientists to start developing systems for marine vessels powered by nuclear energy in response to U.S. violation of its atomic deal with world powers.

Nuclear experts stated that President Hassan Rouhani's move would probably require Iran to enrich uranium to a fissile purity above the maximum level set in the nuclear deal to allay fears of Tehran building an atomic bomb.

Rouhani's announcement marked Tehran's first concrete reaction to a decision by the U.S. Congress last month to extend some sanctions on Tehran that would also make it easier to re-impose others lifted under the nuclear pact.

The White House said it was aware of Iran's order and noted that Rouhani had said any such work on the vessels would be done within the framework of Iran's commitments.

White House spokesman Josh Earnest told a news briefing, "The announcement from the Iranians today does not run counter to the international agreement to prevent Iran from obtaining a nuclear weapon."

U.S. State Department spokesman John Kirby said the United States was confident the International Atomic Energy Agency, which inspects Iran's nuclear sites, would be able to analyze Iran's compliance with the deal.

Kirby said, referring to Rouhani's announcement, at a news briefing on Tuesday, "There's a lot we don't know about it, what it means."

A marine nuclear propulsion program is a "massive undertaking for any nation" and would likely take decades to realize, he added.

Rouhani's words could stoke tensions with Washington, already heightened by U.S. President-elect Donald Trump's vow to scrap the deal, under which Iran curbed its nuclear fuel production activities in exchange for relief from economic sanctions.

Rouhani also ordered planning for production of fuel for nuclear-powered marine vessels "in line with the development of a peaceful nuclear program of Iran."

But under the nuclear settlement Iran reached with the United States, France, Germany, Britain, Russia and China, it is not allowed to enrich uranium above a 3.67 percent purity for 15 years, a level unlikely to be enough to run such vessels.

"On the basis of international experience, were Iran to go ahead with such a (nuclear propulsion) project, it would have to increase its enrichment level," said Mark Hibbs, nuclear expert and senior fellow at Carnegie Endowment for International Peace.