WASHINGTON - As arguments flare in Israel and the United States about a possible military strike to set back Iran's nuclear program, an accelerating covert campaign of assassinations, bombings, cyberattacks and defections appears intended to make that debate irrelevant, according to current and former American officials and specialists on Iran.
The campaign, which experts believe is being carried out mainly by Israel, apparently claimed its latest victim on Wednesday when a bomb killed a 32-year-old nuclear scientist in Tehran's morning rush hour.
The scientist, Mostafa Ahmadi Roshan, was a department supervisor at the Natanz uranium enrichment plant, a participant in what Western leaders believe is Iran's halting but determined progress toward a nuclear weapon. He was at least the fifth scientist with nuclear connections to be killed since 2007; a sixth scientist, Fereydoon Abbasi, survived a 2010 attack and was put in charge of Iran's Atomic Energy Organization.
Iranian officials immediately blamed both Israel and the United States for the latest death, which came less than two months after a suspicious explosion at an Iranian missile base that killed a top general and 16 other people. While American officials deny a role in lethal activities, the United States is believed to engage in other covert efforts against the Iranian nuclear program.
The assassination drew an unusually strong condemnation from the White House and the State Department, which disavowed any American complicity. The statements by the United States appeared to reflect serious concern about the growing number of lethal attacks, which some experts believe could backfire by undercutting future negotiations and prompting Iran to redouble what the West suspects is a quest for a nuclear capacity.
"The United States had absolutely nothing to do with this," said Tommy Vietor, a spokesman for the National Security Council. Secretary of State Hillary Rodham Clinton appeared to expand the denial beyond Wednesday's killing, "categorically" denying "any United States involvement in any kind of act of violence inside Iran."
"We believe that there has to be an understanding between Iran, its neighbors and the international community that finds a way forward for it to end its provocative behavior, end its search for nuclear weapons and rejoin the international community," Mrs. Clinton said.
The Israeli military spokesman, Brig. Gen. Yoav Mordechai, writing on Facebook about the attack, said, "I don't know who took revenge on the Iranian scientist, but I am definitely not shedding a tear," Israeli news media reported.
Like the drone strikes that the Obama administration has embraced as a core tactic against Al Qaeda, the multifaceted covert campaign against Iran has appeared to offer an alternative to war. But at most it has slowed, not halted, Iran's enrichment of uranium, a potential fuel for a nuclear weapon. And some skeptics believe that it may harden Iran's resolve or set a dangerous precedent for a strategy that could be used against the United States and its allies.
Neither Israeli nor American officials will discuss the covert campaign in any detail, leaving some uncertainty about the perpetrators and their purpose. For instance, Karim Sadjadpour, an Iran expert at the Carnegie Endowment for International Peace, said he believed that at least some of the murdered scientists might have been killed by the Iranian government. Some of them had shown sympathy for the Iranian opposition, he said, and not all appeared to have been high-ranking experts."I think there is reason to doubt the idea that all the hits have been carried out by Israel," Mr. Sadjadpour said. "It's very puzzling that Iranian nuclear scientists, whose movements are likely carefully monitored by the state, can be executed in broad daylight, sometimes in rush-hour traffic, and their culprits never found."
A more common view, however, is expressed by Patrick Clawson, director of the Iran Security Initiative at the Washington Institute for Near East Policy. "I often get asked when Israel might attack Iran," Mr. Clawson said. "I say, 'Two years ago.' "
Mr. Clawson said the covert campaign was far preferable to overt air strikes by Israel or the United States on suspected Iranian nuclear sites. "Sabotage and assassination is the way to go, if you can do it," he said. "It doesn't provoke a nationalist reaction in Iran, which could strengthen the regime. And it allows Iran to climb down if it decides the cost of pursuing a nuclear weapon is too high."
A former senior Israeli security official, who would speak of the covert campaign only in general terms and on the condition of anonymity, said the uncertainty about who was responsible was useful. "It's not enough to guess," he said. "You can't prove it, so you can't retaliate. When it's very, very clear who's behind an attack, the world behaves differently."
The former Israeli official noted that Iran carried out many assassinations of enemies, mostly Iranian opposition figures, during the 1980s and 1990s, and had been recently accused of plotting to kill the Saudi ambassador to the United States in Washington.
"In Arabic, there's a proverb: If you are shooting, don't complain about being shot," he said. But he portrayed the killings and bombings as part of a larger Israeli strategy to prevent all-out war.
By SCOTT SHANE
Published: January 12, 2012