"The Secretary General has consistently reiterated that the Joint Comprehensive Plan of Action represents a major achievement in nuclear nonproliferation and diplomacy and has contributed to regional and international peace and security," Farhan Haq said in a news conference.
The landmark agreement between Iran and the P5+1 group of nations -- the five permanent UN Security Council members and Germany -- imposed strict curbs on Tehran’s nuclear program in return for the lifting of longstanding U.S. sanctions.
Iran's President Hassan Rouhani threatened Wednesday to depart from the deal within 60 days if Tehran's interests were not protected.
Iran is also prepared to resume its uranium-enrichment activities whenever necessary, according to the head of Iran’s Atomic Energy Agency Ali Akbar Salehi.
"[Guterres] strongly hopes that Joint Comprehensive Plan of Action can be preserved," Haq said.
Last year, U.S. President Donald Trump withdrew Washington from the nuclear deal, and what followed was a "maximum pressure" campaign, with the Trump administration re-imposing economic sanctions on Iran’s energy and banking sectors. Washington also ended sanctions waivers for countries buying Iranian oil.
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