If the U.S. does not take forceful action to check Tehran’s progress toward a nuclear bomb, Israel will. That’s a much more dangerous scenario.

By Dennis Ross

While the international community was focused on the anniversary of Russia’s invasion of Ukraine, inspectors from the United Nations’ nuclear watchdog, the International Atomic Energy Agency (IAEA), discovered uranium residue enriched to 84 percent in Iranian centrifuge cascades. Weapons-grade fissile material is typically characterized as uranium enriched to 90 percent, but it is worth recalling that the U.S. atomic bomb dropped on Hiroshima in August 1945 was a fission weapon enriched to an average of 80 percent. The Iranians may claim that they are not enriching beyond 60 percent, and that these are mere particles, but the discovery should set off alarm bells.

It is a reminder that Iran has achieved the capacity to produce weapons-grade material very quickly. Enriching to 60 percent—something that the IAEA’s director, Rafael Grossi, says has “no justification for civilian purposes”—has already put the Iranians in that position. Granted, creating weapons-grade fissile material is not the same as having a bomb, but it is the most important element needed for bomb-making. The IAEA may not know yet whether the 84 percent is simply a limited residue from the cascades or whether this was a deliberate move by the Iranians to enrich to near weapons-grade. But we do know that, for the second time in a month, Iran has engaged in suspicious activity at an enrichment site. At Fordow, the Iranians connected two clusters of advanced centrifuges enriching uranium to 60 percent and did not inform the IAEA that it had done so. This is contrary to their obligations under the terms of the nuclear-nonproliferation treaty. Now there is also the 84 percent finding.

Regardless of the Iranian explanation, Iran is drawing closer to enriching to weapons-grade, and on its current pace could easily accumulate 10 bombs’ worth of fissile material enriched to 60 percent by the end of this year. And a senior defense official this week suggested that it would take the Iranians less than two weeks to make such material weapons-grade. Two implications of this emerging reality need to be considered. First, the Iranians are acting as if enriching to near weapons-grade and accumulating large amounts of fissile material pose no risk to them. And second, the idea that Israel will sit back and not act against what its leaders view as an existential threat is an illusion.

Israel may be preoccupied with the Netanyahu government’s judicial-overhaul plan and the growing levels of violence with the Palestinians, but Israeli leaders from across the political spectrum share the prime minister’s concerns about the quantity of bomb-making fissile material that Iran is accumulating and the hardening of its nuclear infrastructure, which will make it more and more difficult for Israel to destroy. Benjamin Netanyahu has already told U.S. officials and French President Emmanuel Macron that if nothing is done soon to stop the advance of the Iranian nuclear program, Israel will have no choice but to attack.

The IAEA’s discovery of the enriched materials will only confirm the deepening Israeli belief that the current approach of the U.S. and its allies will eventually result in Iran getting a bomb, and that, regardless of statements to the contrary, America and the international community are prepared to live with that outcome. Israel, however, is not.

If the Biden administration wants to force the Iranians to recognize the dangerous risk they are running and convince the Israelis that it has a way to deter the Iranians from advancing their program, it must respond to the recent revelation. The Iranians, the Israelis, and others in the region will certainly be watching to see what the U.S. does.

To be effective, that response should be shaped by a four-part strategy. First, the Biden administration must alter its declaratory policy. Saying that “every option remains on the table,” as Secretary of State Antony Blinken did in an interview, impresses no one, least of all the Iranians. Instead, Blinken or President Joe Biden should announce that although the U.S. favors diplomacy for resolving the threat of the Iranian nuclear program, the Iranians continue to demonstrate that they don’t; instead, their actions are drawing them closer and closer to a bomb, something that the U.S. has pledged to prevent, and Iran must understand that its actions jeopardize its entire nuclear infrastructure, including parts that could in theory be used for civilian energy purposes. Declaring this would signal that the U.S. is beginning to prepare the American public and the international community for possible military action against Iran’s nuclear program.

Second, to give these words force, the Iranians need to see the U.S. rehearsing its own air-to-ground attacks in exercises in the region. The recent major joint exercise with Israel was a good first step. It needs to be repeated. Parallel to this, the Biden administration should be visibly engaging with the Israelis, Saudis, Emiratis, and others on consultations and exercises designed to blunt any possible Iranian attacks against those countries. This would demonstrate that the administration is not only preparing for a possible attack, but also anticipating how the Iranians might retaliate against American allies in the region—and how the U.S. has planned to foil that.

Third, Tehran is under two misapprehensions: It does not believe that we will act militarily against Iran, and it thinks we will also stop the Israelis from doing so. The administration can counter that impression by providing material and munitions that would make any Israeli strikes more effective. Given the distances involved and the lack of access to forward bases, Israel needs refueling tankers so that it can hit fortified Iranian targets multiple times. It has contracted for four Boeing KC-46A air tankers, but the first is not scheduled for delivery until late 2025. The Biden administration can ensure that the Israelis are first in line, enabling tankers to arrive this year. The U.S. can also provide more powerful munitions than the ones Israel currently has for collapsing hardened targets. This unusual move of providing Israel with such specific military assistance would send a message loud and clear: Far from holding the Israelis back, the U.S. will support them.

Fourth, the Biden administration must also act in a way that is out of character in Iranian eyes. Over the past month, America’s forces in Syria were targeted twice by Iranian Shiite-militia proxies. In neither case did the U.S. retaliate. The Iranians need to see something they do not expect—a military response showing that whatever constraints were previously observed now no longer apply. Proxy attacks must be answered, without hesitation and disproportionately. Such action could include, for example, unacknowledged U.S. air strikes on the camps in Iran where these militias are trained. If the U.S. does not claim responsibility, the Iranians would not be forced to respond—but they would get the point.

If the U.S. adopts all of these measures, the Iranians would take notice. The aim would be to get the Iranians to stop the advance of their nuclear-enrichment program, and in so doing reopen the possibility of a diplomatic pathway to reverse it.

Is such an approach free of risk? No. Iran may test us to see how serious we are. The Islamic Republic’s leaders may say that they will walk away from the nonproliferation treaty, and so deny the IAEA any access at all. But this much is certain: For the U.S. to hold to the current policy will do nothing to alter Iran’s progress toward the moment when it can choose to go for a bomb—and Israel is simply not going to wait for that.

Without a clear show of resolve by the U.S. to act on its own behalf, unilateral Israeli strikes on the Iranian nuclear program will trigger Hezbollah and maybe Hamas missile attacks on Israel, potentially numbering thousands per day. Iran itself may launch retaliatory attacks against the Saudis and other regional adversaries, in an effort to show that if Iran pays a price, everyone will pay a price. If the Biden administration does not change course, there is a good chance it will face a regional conflict in the Middle East.

To avoid a war with a threatening adversary, that adversary has to believe you will use force. A clear signal of a new American approach may now be essential not only to persuade the Iranians to stop their advance toward a nuclear weapon, but also to show China and Russia that the U.S. is capable of dealing with multiple threats at once and that it has the will to do so. As well as deterring the Iranians, the Biden administration can alter the calculus of the Chinese and Russians over expansionist plans in other parts of the world.

Dennis Ross, a former special assistant to President Barack Obama, is the counselor and William Davidson Distinguished Fellow at the Washington Institute.