Iran shipped 25,000 pounds of low-enriched uranium to Russia on Monday, the United States said, hailing a key step in Tehran's implementation of a historic nuclear accord.
"I am pleased to report that we have seen important indications of significant progress towards Iran completing its key nuclear commitments under the deal," Secretary of State John Kerry said.
Under a deal struck in July between Iran and the P5+1 group of world powers, Tehran agreed to scale back its nuclear program so that Washington and its allies are assured it is no longer on the threshold of being able to make an atomic bomb.
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The International Atomic Energy Agency, the UN nuclear watchdog, will decide when Tehran has complied with its obligations, after which the United States and other world powers will begin to dismantle the economic sanctions that targeted the program.
Welcoming Monday's shipment, Kerry said that by divesting itself of this low-enriched material, Iran had already tripled 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 percent 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."