Iran has transferred most of its enriched uranium to Russia, meeting a key obligation taken on by Tehran under the nuclear deal reached in July with six world powers, reports AFP.

The United States said Monday that Iran has shipped 25,000 pounds of low-enriched uranium to Russia. "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, according to The Associated Press.

Under the nuclear agreement between Iran and the P5+1 nations, Iran agreed to significantly scale back its nuclear program to ensure world powers that it is no longer pursuing a nuclear bomb, which it denies it was doing in the first place.

Iran is only allowed to keep 600 pounds of the nine tons of low-enriched uranium it has stockpiled. The uranium is normally used for power generation but can be further enriched and used to arm nuclear weapons.

Kerry said that by shipping most of its low-enriched uranium to Russia, Iran has already tripled the amount of time it would take to make enough fuel for a nuclear bomb, from three months to nine months. "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," Kerry 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."

Iran must also deactivate about half of its centrifuges used to enrich uranium and shut down its only reactor capable of creating plutonium, according to The New York Times. The United Nations' nuclear watchdog, the International Atomic Energy Agency, says Iran is working on both of those measures.

Once the IAEA confirms that Tehran has complied with the terms of the agreement, the U.S. and other world powers will remove crippling economic sanctions, which is expected to happen next month.