ISTANBUL — Days after the assassination of top Iranian nuclear scientist Mohsen Fakhrizadeh, competing camps in Iran are wielding his memory in a battle over the country's political future and how it should deal with the United States.

President Hassan Rouhani’s reformist camp seems eager to claim him, seeking a postmortem endorsement for engagement with the West. In old photographs publicized Tuesday, Fakhrizadeh is seen receiving state honors from Rouhani for helping to secure the 2015 nuclear deal that Iran signed with the United States and other world powers.

The same day, however, previously unreleased audio was aired with the scientist purportedly questioning the utility of negotiations with the United States. “America can’t be compromised with,” Fakhrizadeh is heard to say, in a recording apparently made this year. It seemed like a reminder from Iranian hard-liners that Fakhrizadeh was really one of theirs.

The dueling messages underscore the intense debate that Fakhrizadeh’s death — in a brazen daylight ambush Friday east of the capital, Tehran — has stirred in his country, including over who was responsible for the security lapses implicated in the killing and its consequences. Most urgent is a dispute over how best Iran should respond — with restraint, fury or something in between.

Arguments over Fakhrizadeh are being wielded like cudgels by conservatives and reformists, squaring off in “the currently very contentious politics of Iran,” said Ali Reza Eshraghi, a visiting scholar at the Center for Middle East and Islamic Studies at the University of North Carolina.

The outcome of these debates could have profound implications for the Biden administration, which hopes to renew nuclear negotiations after four years of President Trump’s “maximum pressure” campaign against Tehran.

Iran’s conservative-dominated parliament responded to the ­killing by passing legislation Wednesday to immediately increase uranium enrichment to levels well above those allowed under the nuclear deal, and to suspend United Nations nuclear inspections if oil and banking sanctions on Iran are not lifted by early February. These steps would probably complicate President-elect Biden’s ambitions to reengage with Iran.

Rouhani pushed back: “Let’s allow the ones who have more than 20 years of experience in diplomacy and have defeated the U.S. many times in the past three years to proceed with care and patience,” he said Thursday during a ceremony at the Energy Ministry.

It remains unclear whether Iran’s leadership will carry out the plan come the February deadline. Even so, Tehran is likely to seek greater concessions from the West in any renewed nuclear negotiations, using Fakhrizadeh’s assassination — a fresh grievance — as leverage, analysts said.

The killing — widely attributed to Israel and seen among Iranians as a flagrant national insult — could also have consequences for a public battered by a year of extraordinary hardships, including the most severe coronavirus outbreak in the Middle East and an economic crisis made worse by a suffocating regime of Western sanctions. In recent days, people have been bracing for further state repression of dissent, “with an excuse of having to be united against a foreign invasive power,” said Amir, a 30-year-old university student studying philosophy in Tehran, who spoke on the condition that only his first name be used out of fear for his security.

Fakhrizadeh was a key figure in Iran’s disbanded nuclear weapons program and one of Iran’s best-guarded officials. The fatal ambush is widely seen as the latest in a string of grave lapses by Iran’s security and intelligence services, including the Islamic Revolutionary Guard Corps (IRGC). The year began with a U.S. drone strike in Baghdad that killed a top IRGC commander, Maj. Gen. Qasem Soleimani, and days later Iranian security forces mistakenly shot down a Ukrainian passenger jet, killing all 176 people aboard. In July, a fire broke out at a nuclear facility that Iranian authorities blamed on “sabotage.” Then in August, Israeli agents acting on behalf of the United States assassinated a senior al-Qaeda official in Tehran.

After Fakhrizadeh’s death, Iranian officials sought to deflect responsibility for security failures. “There is a kind of blame game going around between the government intelligence ministry and IRGC intelligence ministry,” two competing parts of Iran's bifurcated political system, said Ellie Geranmayeh, deputy director of Middle East and North Africa programs at the European Council on Foreign Relations.

As news of the ambush spread, Iranian media outlets, based on eyewitnesses, reported that up to 12 perpetrators could have been involved and then escaped. By Monday, officials were pushing a new narrative seemingly intended to save face: The attack was “a very complicated assassination that was carried out remotely with electronic devices,” Ali Shamkhani, secretary of the Supreme National Security Council of Iran, told state television, ­according to the Reuters news agency.

The killing has “increased the heat from the more conservative end” of Iran’s political system on Rouhani, who represents a camp more open to nuclear negotiations with Western powers. “There is a lot of backlash currently in Iran about the need to retaliate, the need to ramp up the nuclear energy program,” said Narges Bajoghli, an Iran expert at the School of Advanced International Studies at Johns Hopkins University.

The parliamentary vote to increase nuclear enrichment and suspend U.N. inspections is the clearest shot yet fired by conservatives.

The legislation was finalized after a back-and-forth with the Guardian Council, which vets such proposals, and gives European countries two months to relieve sanctions and provide access to international banking systems. That is a challenging timeline with President Trump still in office until January.

Rouhani’s government is technically obliged to implement the legislation. But Iran’s nuclear file is under the authority of the Supreme National Security Council, a body made up of military and political leaders that ultimately reflects the preferences of Ayatollah Ali Khamenei, the country’s supreme leader. Come February, the council will decide whether to proceed with the plan, said Geranmayeh. For now, the legislation remains symbolic, a show of strength that ramps up pressure on Rouhani’s camp.

Either way, the legislation and the attention it received were “indicative of the wider debate that’s going on” over whether the assassination provided further leverage Iran could use in its negotiations with the United States, Bajoghli said.

None of Iran’s most influential political factions argued against negotiations with the West, which could bring an end to crippling U.S. sanctions imposed after the Trump administration unilaterally walked away from the 2015 nuclear agreement, said Geranmayeh. But there was “considerable disagreement whether Iran under Rouhani . . . risks being duped again by America,” she said.

The assassination of Fakhrizadeh now threatens to further widen the gap between Iran and the United States, said Afshon Ostovar, an associate professor of national security affairs at the U.S. Naval Postgraduate School.

There is a growing consensus in the United States that issues apart from Iran’s nuclear program — such as its ballistic missile development and support for proxy militias elsewhere in the region — may need to be part of any future agreement. On the other side, Iran believes that any deal “needs to be weaker and come with more inducements than the first one,” he said.

With Iran scheduled to hold a presidential election this spring, some analysts predict that hard-line factions could prevail and consolidate their grip on power, further complicating Biden’s hopes for reviving diplomacy with Tehran. “I think some windows of opportunities are closing,” Eshraghi said.

While it could be easier for the Biden administration to negotiate with reformists, a victory by the conservatives would not necessarily bring diplomacy to a halt. A more hard-line government in Iran “might allow for a slower rapprochement — but at the same time, one that might last longer,” Eshraghi said.

“There has been a lot of talk inside Iran that Rouhani should not be in charge of these negotiations — it’s a lame-duck administration” — and that negotiations be handled by the Supreme National Security Council instead, he said.

One wild card is the possibility that the Trump administration or allies such as Israel could carry out another attack in the coming weeks, perhaps to preempt a new diplomatic push by the Biden team.

“So far, and I think that this is going to continue to be the case, the Iranian establishment all across the board has determined that they will continue with ‘maximum restraint,’ as they call it,” Bajoghli said.

Other analysts are not so sure.

In the days before Fakhrizadeh’s killing, a prisoner swap raised hopes for an easing of international tensions. Iran had freed an imprisoned Australian academic, apparently in exchange for three Iranian operatives who had been jailed in Thailand since 2012 over a botched plot to kill Israeli diplomats.

Those operatives had been on a mission to retaliate for Israel’s earlier assassinations of nuclear scientists, but had failed. Their return to Iran, to a heroes’ welcome, was viewed as an achievement by Iran’s security and intelligence agencies, and “had kind of closed that circle of the shadow war against the nuclear program,” Ostovar said.

Fakhrizadeh’s killing may have given Iran a new score to settle.

“How does Iran handle this? What do they do? There is no way you want it to continue happening,” he said.

Berger reported from Beirut.