WASHINGTON — Long-running differences over how to deal with Iran’s nuclear program have erupted into new tensions between the Biden administration and Israel, with two senior Israeli officials leaving Washington this week concerned that the Americans’ commitment to restoring the 2015 nuclear deal will lead to a flawed agreement allowing Tehran to speed ahead with its nuclear enrichment program.
The strains were evident all week, as the Biden administration sought to bring the alliance with Israel into a united front about how to deal with Iran over the next year.
In an effort to close the gap, American officials let out word this week that two months ago, Mr. Biden asked his national security adviser, Jake Sullivan, to review the Pentagon’s revised plan to take military action if the diplomatic effort collapsed. Administration officials also outlined new efforts to tighten, rather than loosen, sanctions on Iran.
Mr. Biden’s focus on military options and sanctions was an effort to signal to Tehran that the United States was running out of patience with Iranian foot-dragging in the nuclear negotiations in Vienna, administration officials said. Secretary of State Antony J. Blinken said last week that the new Iranian government “does not seem to be serious about doing what’s necessary to return to compliance” with the 2015 nuclear deal.
But the tougher line was also aimed at calming increasingly frustrated Israeli officials. Though they will not criticize the American president in public the way former Prime Minister Benjamin Netanyahu did during the Obama administration, Israeli officials in private argue that the Iranians are advancing their nuclear program while betting that the United States, eager to diminish American commitments in the Middle East, will not abandon the Vienna talks for more forceful action.
This article is based on discussions with more than a dozen American and Israeli officials who spoke on the condition they be granted anonymity to discuss both sensitive matters of diplomacy and classified intelligence assessments.
After a tense phone call with Mr. Blinken 10 days ago, the Israeli prime minister, Naftali Bennett, dispatched his defense minister, Benny Gantz, and the new head of the Mossad, David Barnea, to Washington this week armed with new intelligence about Iranians’ uranium enrichment and the work of what Israel says is their weapons group. Despite the tougher American talk, Israeli officials left worried that the diplomatic outreach to Iran would continue.
The disagreement over Iran is just one of several issues troubling the Biden-Bennett relationship. The pair started off on a strong footing: Mr. Biden spoke with Mr. Bennett within hours after the Israeli leader took office in June — a signal of support given that Mr. Biden had taken weeks after his inauguration to speak directly with Mr. Bennett’s predecessor, Mr. Netanyahu.
But the two governments have since clashed on whether the U.S. should reopen the American consulate to the Palestinians in Jerusalem, which was closed by President Donald J. Trump. Mr. Bennett says such a move would undermine Israel’s sovereignty in its capital city.
There are also disagreements over Israeli plans to expand its settlements in the occupied West Bank, and over the Biden administration’s decision to blacklist two Israeli spyware firms, NSO Group and Candiru, whose products, the U.S. alleges, have been used by authoritarian governments to hack the phones of dissidents and rights activists.
But at the heart of the tensions between Israel and the United States is the fundamental disagreement over how to stop the Iranian program. It is not a new argument: The two allies fought bitterly over the 2015 agreement, which Israel opposed and President Barack Obama signed.
More recently, they have disagreed about the wisdom of Israeli sabotage of Iranian facilities, which Mr. Bennett’s government believes has set back the program, and which some in the United States argue only encourages the Iranians to build back the nuclear enrichment facilities with more efficient, up-to-date equipment.
Israeli officials had been happy with the warm welcome the White House offered Mr. Bennett. The Biden administration had praised his government for being far more transparent with it than Mr. Netanyahu had been. Indeed, the Israelis consulted with the Americans before launching two covert strikes against Iran, one in September against a missile base and one in June against an Iranian factory building nuclear centrifuges, according to people briefed on the actions.
But the call between Mr. Bennett and Mr. Blinken last week was contentious, with the two sides embracing very different opinions about the value of a renewed agreement to check Tehran’s nuclear ambitions. The call left officials in both countries frustrated, according to officials from both countries.
During the phone call, Mr. Bennett said that Iran was trying to blackmail the United States by increasing the enrichment percentage, according to an official familiar with details of the call. Mr. Bennett added that no official, American or Israeli, wants to be the one to report that Iran has reached bomb-grade enrichment, but fears of a nuclear-armed Iran should not lead to surrendering to Iranian demands or signing a reckless agreement.
Some American officials believe those concerns about concessions are misplaced. Israeli officials had complained that the United States was considering offering an interim deal with Tehran that would roll back some sanctions in return for a freeze on some of its nuclear activity. But American officials say such an offer is not actively being considered, at least for now, because of Iran’s unwillingness to engage.
Israeli officials have not been reassured. They are increasingly concerned that the United States will eventually reach a deal with Tehran and then seek to block Israeli intelligence services from carrying out covert sabotage attacks. Israeli leaders say they want a guarantee from the Biden administration that Washington will not seek to restrain their sabotage campaign, even if a renewed nuclear deal is reached.
Disagreements over intelligence assessments about the Iranian nuclear stockpile and bomb-making know-how remain relatively small, mostly focused on how long it would take Iranians to produce a weapon if they get enough bomb-grade nuclear fuel.
But the gulf about the meaning of those assessments is wide. American officials believe that so long as Iran has not moved to develop a bomb it does not have a nuclear military program, since it suspended the existing one after 2003. Israeli officials, on the other hand, believe that Iran has continued a clandestine effort to build a bomb since 2003.
Some Israeli officials believe that the sabotage campaign is having strategic effects and could be one of the reasons Iranians, however tentatively, have returned to Vienna. A senior Israeli intelligence official said the sabotage operations had created crippling paranoia at the top of the Iranian government. The operations, the official said, have caused Tehran to rethink whether it should accelerate the nuclear project.
But even American supporters of the Israeli approach say it is akin to “mowing the grass,” a necessary step to keep Iran in check but not one that will ever fully halt Tehran’s nuclear research. These American officials believe that the only durable way to prevent Iran from developing a weapon is to reach an agreement, like the one in 2015, that requires Iran to ship its nuclear fuel out of the country. And that would require significant sanctions relief in return.
In the meetings this week, Israeli officials tried to persuade Washington not to work toward a diplomatic agreement and to instead tighten sanctions. But Israeli officials say they fear that the U.S. is conducing secret back-channel communication with Iran, and that a new round of talks in Vienna will eventually lead to the signing of a deal.
The meetings came against the backdrop of a recent Iranian attack on American forces in Syria, a senior American official said. The Israelis, the official said, had an aggressive attitude on the Iranian threat, related to both the nuclear program and the risk of missile and other weapon proliferation.
But there is a growing American concern that it is just a matter of time before an American service member is killed or wounded by an Iranian proxy drone strike on Mr. Biden’s watch. With Iran making clear it will retaliate against American personnel in Syria or Iraq if Israel strikes Iran or its proxies, it complicates strike planning.
In an appearance at The Wall Street Journal’s CEO Council on Monday, William J. Burns, the C.I.A. director, raised concerns about the Iranian nuclear work. He said the Iranians were “dragging their feet” on negotiations as they were “making steady advances in their nuclear program, particularly enrichment to 60 percent now as well.” That is the closest the Iranians have ever come to bomb-grade fuel, which is usually defined as 90 percent purity.
But, Mr. Burns added, the United States continues to believe that Iran has not made a decision to weaponize its nuclear program.
Patrick Kingsley contributed reporting from Jerusalem, and Eric Schmitt from Washington.