Iran sent a major shipment of low-enriched uranium materials to Russia on Monday, a key step in Tehran’s implementation of this year’s historic nuclear accord with world powers.

Iran sent a major shipment of low-enriched uranium materials to Russia on Monday, a key step in Tehran's implementation of this year's historic nuclear accord with world powers.

The United States hailed the move, which Secretary of State John Kerry said marked "significant progress" in Tehran's fulfillment of a deal to stop it developing nuclear weapons.

The Russian foreign ministry confirmed the report after Ali Akbar Salehi, head of Iran's Atomic Energy Organization, told the ISNA news agency: "The fuel exchange process has taken place."

According to ISNA's report, Iran had sent 8.5 tons of low-enriched nuclear material to Russia and received "around 140 tons of natural uranium in return."

Washington described the shipment as 25,000 pounds of "low-enriched uranium materials."

Under the deal struck in July in Vienna between Iran and the P5+1 group of world powers, Tehran agreed to cut its low-enriched uranium stockpile to less than 300 kilograms (660 pounds).

After Iran's compliance has been verified, the United States and its allies will begin to dismantle the sanctions imposed on Tehran in response to its nuclear program.