A ship carrying 25,000lb (11,000kg) of low-enriched uranium left Iran for Russia on Monday, marking one of the most vital steps yet in a high-stakes deal to deny Iran a nuclear weapon.



“I am pleased to report that we have seen important indications of significant progress towards Iran completing its key nuclear commitments under the deal,” the US secretary of state, John Kerry, said.

The July accord has been trumpeted as one of the banner foreign policy achievements of Barack Obama’s presidency but proved divisive in Washington, with Republicans refusing to support it and several of the party’s presidential candidates vowing to scrap it.

Under the deal between Iran and the P5+1 group of world powers, Tehran agreed to scale back its nuclear programme so that Washington and its allies were assured it would no longer be on the threshold of being able to produce an atomic weapon. In return, Tehran will have access to about $100bn of previously frozen assets and fully return to the oil market.

Iran had until the end of 2015 to ship out all but 660lb (300kg) of the low-enriched uranium it has stockpiled. Low-enriched uranium is suited to power generation but can be further enriched to yield fissile material for nuclear warheads.

Welcoming Monday’s shipment, Kerry said that by divesting itself of this low-enriched material, Iran had already trebled the amount of time it would take to produce enough fuel for a bomb from two or three months up to nine.

“The shipment included the removal of all of Iran’s nuclear material enriched to 20% that was not already in the form of fabricated fuel plates for the Tehran Research Reactor,” he said.

“This removal of all this enriched material out of Iran is a significant step toward Iran meeting its commitment to have no more than 300 kilograms of low-enriched uranium by Implementation Day.”

Kerry praised Russia, “a country with significant experience in transporting and securing nuclear material”, for taking the material out of Iran and providing natural uranium in exchange.

The July agreement also commits Iran to sharply reduce the number of centrifuges, which are used to enrich uranium, as well as to re-engineer a reactor to cut its output of plutonium – another pathway to nuclear weapons.

The International Atomic Energy Agency, the UN nuclear watchdog, will decide when Tehran has complied with its obligations, after which the US, Russia, China, Britain, France and Germany will remove some economic sanctions that targeted the programme.

Ben Cardin, the top Democrat on the Senate foreign relations committee, said recently that “implementation day” could come earlier than expected, perhaps even next month, and not in the spring as initially expected.

But the deal has suffered a potential threat in a different area. Earlier this month the US Congress passed a law restricting visa-free travel rights for people who have visited Iran or hold dual Iranian nationality. The measure, which affects citizens of the 38 mostly European countries that have visa waiver arrangements with the US, is framed as a counter-terrorism measure and also targets Iraq, Syria and Sudan.

Asked about the US law on Monday, the Iranian foreign ministry spokesman, Hossein Jaberi Ansari, told a press conference: “Any steps taken outside the agreement are unacceptable to Iran, and Iran will take its own steps in response where necessary.”

Tehran recently test-fired two ballistic missiles capable of carrying a nuclear warhead in breach of a UN security council resolution, in what some analysts say is part of a backlash aimed at showing a domestic audience that it has not caved in to the US.

