How should the United States respond to Iran’s July 31 drone attack on the Mercer Street, a Japanese-owned, Liberian-flagged, Israeli-managed oil products tanker in international waters off the coast of Oman, killing the Romanian captain and a British crewmember? The United States was obviously not a direct target of the Iranian attack. But Washington, together with other maritime powers, is the ultimate guarantor of freedom of navigation in the world’s oceans—a vital U.S. interest. The United States shares with other countries responsibility for protecting this essential principle, deterring assaults on it, and punishing egregious violations.
At the same time, the ship attack is, of course, part of the broader gray-zone campaigns Iran is waging in multiple arenas with the United States and—sometimes separately, sometimes jointly—with Israel. And it would be unwise to delink either the ship attack or the gray-zone campaign from the ongoing negotiations between Iran, the United States, and other powers over a possible return to the 2015 Iran nuclear deal, known as the Joint Comprehensive Plan of Action (JCPOA).
There is undoubtedly a debate underway in Washington about these linkages and how any response to the ship attack will impact the JCPOA talks. The U.S. decision to identify Iran as the culprit on Aug. 1 and promise, in the words of U.S. Secretary of State Antony Blinken, “an appropriate response,” reflects an important stage in the debate over how Washington should act.
It is likely that some key officials in the Biden administration believe that publicly identifying Iran is a major U.S. step in itself. By this line of thinking, any U.S. role in responding to Iran’s attack by targeting Iranian assets—openly or clandestinely, through military action, cyberwarfare, or other means—would constitute a return to direct U.S.-Iranian confrontation last seen with the United States’ killing of Iranian Maj. Gen. Qasem Soleimani in January 2020 in retaliation for attacks on U.S. targets in Iraq.
Any such escalation, so this line of reasoning goes, would risk confirming to Iran’s leadership that Washington was not interested in serious diplomacy and could not be trusted. To avoid this risk, the proponents of this approach would presumably prefer to applaud from the sidelines some appropriate Israeli response to the attack and limit U.S. efforts to diplomatic declarations rather than have the United States be involved in any action.
However, some senior officials are sure to appreciate that fingering Iran publicly as the culprit in the shipping attack will only raise expectations for a more substantive U.S. response. They will recognize the loss of U.S. deterrent power if a deadly attack on civilian shipping is not met with a forceful response.
Missing in this back-and-forth is recognition of the impact of a strong, effective response on the Iran nuclear negotiations. Far from derailing a possible deal, as some in the White House surely worry, a U.S. response to the attack would remove one of the main reasons the talks are stuck. Right now, there are at least four reasons why an agreement with Iran hasn’t been reached, despite U.S. President Joe Biden’s public commitment to achieve a deal. A U.S. response to the Mercer Street attack should shrink that number to three.
Why no deal? First, Iran’s financial troubles have eased. Starting in 2020, during the days of then-U.S. President Donald Trump’s “maximum pressure” campaign, and continuing throughout the Biden administration, a sharp and sustained rise in both the oil price and the volume of Iranian crude exports gave Tehran billions of dollars in unanticipated revenue, lessening the economic urgency of a nuclear agreement that would remove many existing sanctions.
Second, Iran recognizes that the economic benefits of a return to the 2015 accord aren’t as great as originally advertised. Even with a new deal, many global banks and companies are likely to be scared away from doing business in Iran. So the incentive to return to the JCPOA, while real, isn’t as substantial as generally thought.
Third, while diplomacy sputters, Iran is making enormous progress in its nuclear program, bringing it to within weeks of what some experts consider “nuclear breakout”—broadly viewed as the capability of building a bomb. While that threshold and the exact status of Iran’s program are a matter of debate, it is beyond dispute that Iran has made significant progress toward a nuclear weapons capability during the last several months.
And fourth, Tehran and its proxies have been aggressively testing the White House—both with attacks on shipping in the Gulf and via proxy attacks by Iranian-backed militias on U.S. targets in Iraq—without learning precisely where Washington draws a line. The most common U.S. response so far has been to hit pro-Iranian militia sites in northeast Syria, which sends a message to Tehran that the United States is avoiding conflict, not deterring it. Until that message is clarified, Iran is likely to continue ratcheting up its attacks.
An effective U.S. response to the Mercer Street attack would affect Iran’s calculus on this fourth issue. Such a response might include coordinated action with partners targeting Islamic Revolutionary Guard Corps naval bases, factories assembling or producing parts for military drones, or facilities supporting the export of weaponry to Iranian proxies in Iraq, Yemen, Syria, or Lebanon. Alternatively, with partner support and participation, Washington might want to target a wider set of Iranian assets to underscore its capabilities and make Tehran uncertain about future U.S. moves. This would be a far cry from pinprick action against proxy groups and mere public declarations, both of which only invite further Iranian testing.
The United States and its partners—which could range from Britain, directly aggrieved by the Mercer Street attack, to Israel and Gulf Arab states—need not crow about delivering an effective response. They would not even have to claim public credit or responsibility; the message would be clear. Such a response would bolster deterrence in this arena. It would signal to U.S. regional allies that shrinking the U.S. military footprint in the Middle East does not mean Washington is shirking its role as a guarantor of international norms, including the all-important freedom of maritime navigation. And of special concern to the Biden administration: An effective response would have the benefit of addressing one of the four reasons for the impasse in JCPOA negotiations.
Some in the Biden administration will make the opposite case—that an effective reply to Iran’s deadly shipping attack will spook the Tehran regime, confirm to the supreme leader and his new president that the United States is a hostile power not to be trusted, and even fuel an escalation of violence and confrontation. This is a legitimate concern. Far more likely, however, is that Iran will view U.S. inaction as an invitation for further testing, itself raising the prospect of even more lethal attacks than the one on the Mercer Street and further poisoning the potential for diplomacy.
Reasonable people can disagree on the wisdom of resurrecting the JCPOA. But if Washington is committed to that course, the tactical path runs through an effective response to the Mercer Street attack. It won’t ensure the success of nuclear diplomacy but will remove one key obstacle to a deal.
Robert Satloff is executive director of The Washington Institute. This article was originally published on the Foreign Policy website.