Starting on Wednesday, he said, Iran would begin to build up its stockpiles of low enriched uranium and of heavy water, which is used in nuclear reactors — including a reactor that could give Iran a source of bomb-grade plutonium. If the Europeans fail to compensate for the unilateral American sanctions, he said, Iran will resume construction of the Arak nuclear reactor, a facility that was shut down, and its key components dismantled, under the deal.
Mr. Rouhani then threatened a potentially more severe step. If the Europeans do not find a way to help Iran “reap our benefits,” especially in petroleum exports and banking transactions, in 60 days Iran will end the limits on the enrichment of uranium, he said. Currently, it is enriching small amounts, and only to a level of 3.67 percent, which is suitable for nuclear power plants — but not for nuclear weapons.
Without economic progress, he said, “we will not consider any limit” on enrichment, suggesting that it could rise to levels closer to something that could be used in weapons. Iran has never been known to produce weapons-grade material.
China, a signatory to the accord, urged restraint on all sides but put the blame for the confrontation squarely on Washington, which it said had escalated tensions. At a press briefing, Geng Shuang, spokesman for the Ministry of Foreign Affairs, praised Iran for adhering to the nuclear agreement that Mr. Trump has abandoned, and reiterated his country’s endorsement of the agreement and opposition to United States sanctions against Iran.
Russia’s foreign minister, Sergey V. Lavrov, at a meeting in Moscow with his Iranian counterpart, Javad Zarif, complained about the “unacceptable situation” created by the “irresponsible behavior of the United States,” but did not respond directly to Mr. Rouhani’s comments.