The Biden administration had warned that the United States would consider any Iranian attempt on Mr. Trump’s life to be “an act of war,” officials said.

Iran’s leaders may seek to prioritise diplomatic solutions with a second Trump administration. It remains to be seen how Trump will approach the country.

Trump’s foreign policy team will seek to ratchet up sanctions on Tehran, including vital oil exports, as soon as the president-elect re-enters the White House in January, people familiar with the transition said.