A ship carrying over 25,000 pounds (11,000 kg) low-enriched uranium materials departed from Iran for Russia, US Secretary of State John Kerry said Monday, calling it "one of the most significant steps Iran has taken toward fulfilling its commitments."

"I am pleased to report that we have seen important indications of significant progress towards Iran completing its key nuclear commitments under the deal," Kerry said in a statement.

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.

Under the nuclear deal reached by Iran and world powers in July, Iran is required to ship out all except 300 kilograms of low-enriched uranium.

Monday's shipment more than triples the previous two- to three-month breakout timeline for Iran to acquire enough weapons grade uranium for one weapon, Kerry said, hailing it "an important piece of the technical equation that ensures an eventual breakout time of at least one year by Implementation Day."

Implementation Day will come when the International Atomic Energy Agency (IAEA) verifies that Iran has completed all of these nuclear commitments, which increase Iran's breakout time to obtain enough nuclear material for a weapon to one year, up from less than 90 days before the July agreement.

In the statement, Kerry commended Russia for playing "an essential role" in making the shipment possible by taking material out of Iran and providing natural uranium in exchange. He added that Kazakhstan, Azerbaijan and Norway also contributed to the effort.

The US will remain vigilant to ensure that the implementation of the nuclear deal "achieves exactly what we set out to do from the very beginning of these negotiations, to ensure that Iran's nuclear program is and always remains exclusively for peaceful purposes," Kerry said.

The P5+1 group, namely the US, Britain, France, China, Russia and Germany, reached the comprehensive nuclear deal with Iran on July 14.

The accord, titled "Joint Comprehensive Plan of Action," would provide sanctions relief for Iran in exchange for limits on its controversial nuclear program.