(CNN) Iran will take another step away from its landmark nuclear accord with world powers, President Hassan Rouhani said on Tuesday, announcing that the country would begin injecting uranium gas into 1,044 centrifuges that had been spinning empty at its Fordow plant.

Injecting the gas is part of the process to enrich uranium, which could ultimately be used to develop a nuclear weapon, though Iran has repeatedly denied it has any ambitions of building a bomb.

The move marks a significant break from the terms of the 2015 accord, known as the Joint Comprehensive Plan of Action (JCPOA). Under the deal, Iran was limited to operating around 5,000 older-model centrifuges.

"Iran will begin gas injection into the Fordow centrifuges as of tomorrow," Rouhani announced in a televised address Tuesday, according to state-run IRNA news agency.

The international community has long been concerned about Fordow as a center where Iran was possibly pursuing a nuclear program, Sanam Vakil, deputy head of the Middle East North Africa Programme at UK think thank Chatham House, told CNN. "Furdow raises eyebrows," she said.

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