Iran says it has begun enriching uranium to 20%, its latest step away from a 2015 international agreement that limited its nuclear program in exchange for sanctions relief.
State media quoted government spokesman Ali Rabiei saying the higher enrichment had begun Monday at the Fordo facility, which is located inside of a mountain.
Previously, Iran had been enriching up to 4.5% percent.
The higher levels raise fears that Iran will work toward building a nuclear weapon, which requires 90% enrichment. Iran has said for years it has no such plans and that its nuclear program is only for peaceful purposes.
Ensuring Iran does not acquire nuclear weapons prompted a group of six world powers to pursue the nuclear agreement that among other restrictions limited uranium enrichment to 3.67%.
Iran’s move is its latest away from the nuclear deal as it seeks to pressure the other signatories, particularly those in Europe, to deliver on promises of sanctions relief.
The United States pulled out of the deal in 2018 and instituted economic sanctions, especially targeting Iran’s key oil sector.
The latest development, which Iran told the U.N.’s atomic watchdog last week it would pursue, also comes weeks ahead of a change in the U.S. presidency.
President-elect Joe Biden has said he would seek to rejoin the nuclear agreement if Iran came back into compliance.