WASHINGTON — Days after President Trump asked for options to take military action against Iran’s major nuclear site, the government in Tehran has sent conflicting signals, taking a major step to speed up its production of nuclear fuel while also offering President-elect Joseph R. Biden Jr. a way to defuse a confrontation.
On Wednesday, the director general of the International Atomic Energy Agency said Iranian engineers had, for the first time, begun to put uranium into next-generation centrifuges that can enrich fuel faster than before. That move is explicitly prohibited in the 2015 nuclear accord, which Mr. Trump abandoned two and a half years ago.
When the agency issued a report last week noting that the high-speed centrifuges had been moved into the Natanz production site, “they had not started operations,” said Rafael Grossi, the head of the inspection agency. “It is now happening.”
The move is something akin to waving a red flag in the faces of Mr. Trump and the Israelis.
But the provocation coincided with Iran’s foreign minister, Mohammad Javad Zarif, appearing to offer Mr. Biden a path for returning both sides to where they were when Mr. Biden left the vice presidency in January 2017.
In a video interview with an Iranian newspaper broadcast on Tuesday, Mr. Zarif described a way for the United States to recommit to United Nations Security Council resolutions on Iran, in return for an Iranian return to the limits imposed by the 2015 nuclear agreement.
“This needs no negotiations and needs no conditions,” Mr. Zarif said, but he offered few other details.
Mr. Zarif appeared to be offering to roll back the advances Iran has made over the past year, during which it has exceeded the production limits in the 2015 accord twelvefold. Mr. Biden, in return, would have to issue an order ending all of the nuclear-related sanctions imposed by Mr. Trump — all of which violated American commitments under the deal.
But other Iranian officials have stopped short of saying they would actually re-enter the nuclear deal as negotiated, and some officials have said the United States would have to pay reparations for oil sales lost because of Mr. Trump’s decision to reimpose sanctions. That would be nearly impossible, as a political matter, for Mr. Biden, whose aides also say the deal must be improved to block pathways to Iran getting enough nuclear material for a weapon after all limitations are lifted in 2030.
Yet a return to the agreement would prohibit the injection of nuclear fuel into the new centrifuges, and require Iran to rid itself of the excess uranium it has added to its stockpile in response to what Mr. Trump has called his “maximum pressure campaign” on Iran.
While Iran’s actions seem contradictory, that is often the nature of Iranian signaling to the United States.
The nuclear program is under the direction of the Islamic Revolutionary Guards Corps, which suffered an explosion at its centrifuge-production facility in July that has been widely attributed to Israel. The Revolutionary Guards opposed the negotiation of the 2015 deal.
Mr. Zarif negotiated that accord, and remains one of its biggest defenders in Tehran. But the government he serves, under President Hassan Rouhani, faces an election next year and could be swept out of office, amid criticism by Iranian hard-liners that the government was duped five years ago, and has seen none of the promised economic benefits of agreeing to give up its nuclear capability.
After the nuclear agency issued a report last Wednesday, showing slow but steady progress in uranium enrichment by Iran, Mr. Trump asked his top aides for options, including possible military strikes. He was dissuaded from striking by a combination of Vice President Mike Pence, Secretary of State Mike Pompeo, the acting secretary of defense, Christopher C. Miller, and Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff.
They warned that a military strike on Natanz — by missile, bombs or cyberattack — could lead to rapid escalation.
In response to Mr. Trump contemplating an attack on Iran’s nuclear facility, a spokesman for Iran’s government, Ali Rabiei, said on Tuesday that Iran would retaliate with “full force.”
Farnaz Fassihi contributed reporting from New York.