The U.S. confirmed Thursday that Iran has poured concrete into the core of the Arak nuclear reactor, making it nearly impossible to produce weapons-grade plutonium at the facility.
This was one of the major issues preventing full implementation of the nuclear agreement Iran signed in July with six world powers, including the United States.
Iranian officials also affirmed that the core of the reactor was taken out.
"The core vessel of the Arak reactor has been removed ... and IAEA [International Atomic Energy Agency] inspectors will visit the site to verify it and report it to the IAEA," a spokesman for Iran's atomic energy organization said on state television Thursday. "We are ready for implementation day of the deal."
U.S. State Department spokesman John Kirby also said implementation day for the nuclear agreement is "very close."
But the IAEA inspectors first must verify Iran is living up to its commitments.
Under the nuclear agreement, the six major powers — Britain, China, France, Germany, Russia and the United States — will lift economic sanctions against Iran in exchange for pledges to cut back its uranium enrichment program and assurances it cannot build a nuclear bomb.
Iran has denied wanting to build atomic weapons, but the sanctions have wrecked the Iranian economy.