Attacking Iran to force it to stop expanding its nuclear program would be a significant blow to Mr. Biden, who wants to revive the 2015 Iran nuclear accord. Such a strike on the eve of a new administration could poison relations with Tehran to such an extent that negotiating a restoration of the deal, or toughening its terms, could be impossible.
Since Mr. Trump dismissed the secretary of defense, Mark T. Esper, and other top Pentagon aides last week, Defense Department and other national security officials have privately expressed worries that the president might initiate operations, whether overt or secret, against Iran or other adversaries at the end of his term. Others have speculated that Mr. Netanyahu, who at various moments has been on the edge of attacking Iran’s nuclear facilities, might seek to act while Mr. Trump is still in office.
While Mr. Trump’s top advisers — including Mr. Pompeo and Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff — argued against a military strike against Iran, top American officials and commanders still warn of Iran’s malign activities.
“For decades, the Iranian regime has funded and supported terrorism and terrorist organizations,” Gen. Kenneth F. McKenzie Jr., the head of the military’s Central Command, said last week on a webinar about the Middle East.
Iranian media describe an explosion and gun battle on a town’s main boulevard.
Iran state media, in descriptions of the attack on Mr. Fakhrizadeh, said it happened on the main tree-lined boulevard in Absard, a countryside escape with majestic mountains, north of the capital, Tehran.
Pictures posted by state and social media of the attack aftermath showed the scientist’s vehicle, a black S.U.V., with its windshield shattered from bullets and the side windows blown out. Blood streaks and shards of glass and metal are scattered on the road.
Residents told state television they heard the sound of a big explosion followed by intense machine gun fire. A Nissan truck was parked on the opposite side of the road, carrying explosives hidden in wood, state television reported. The truck exploded ahead of Mr. Fakhrizadeh’s car and then a group of five or six gunmen sitting in another car on the same side as Mr. Fakhrizadeh’s vehicle emerged and opened fire on his car, the report said.