Part of the updated planning appears to focus on what military action the United States might take if Iran resumes its nuclear fuel production, which has been frozen under the 2015 agreement. It would be difficult for the Trump administration to make a case that the United States was under imminent nuclear peril; Iran shipped 97 percent of its fuel out of the country in 2016, and currently does not have enough to make a bomb.

That could change if Iran resumes enriching uranium. But it would take a year or more to build up a significant quantity of material, and longer to fashion it into a weapon. That would allow, at least in theory, plenty of time for the United States to develop a response — like a further cutoff of oil revenues, covert action or military strikes.

The previous version of the Pentagon’s war plan included a classified subset code-named Nitro Zeus, a cyberoperation that called for unplugging Iran’s major cities, it power grid and its military.

The idea was to use cyberweapons to paralyze Iran in the opening hours of any conflict, in hopes that it would obviate the need to drop any bombs or conduct a traditional attack. That plan required extensive presence inside Iran’s networks — called “implants” or “beacons” — that would pave the way for injecting destabilizing malware into Iranian systems.

Two officials said those plans have been constantly updated in recent years.

But even a cyberattack, without dropping bombs, carries significant risk. Iran has built up a major corps of its own, one that successfully attacked financial markets in 2012, a casino in Las Vegas and a range of military targets. American intelligence officials told Congress in January that Iranian hackers are now considered sophisticated operators who are increasingly capable of striking United States targets.

Since Mr. Bolton became national security adviser in April 2018, he has intensified the Trump administration’s policy of isolating and pressuring Iran. The animus against Iran’s leaders dates back at least to his days as an official in the George W. Bush administration. Later, as a private citizen, Mr. Bolton called for military strikes on Iran, as well as regime change.

The newly updated plans were not the first time during the Trump administration that Mr. Bolton has sought military options to strike Iran.