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Simultaneously, the U.S. has developed the ability to globalize unilateral sanctions. Washington doesn’t need the support of its allies to isolate Tehran economically, because “secondary sanctions” can effectively compel other countries to comply with the U.S. effort. That the administration has accomplished this while also engaged in trade battles with nearly every important American trading partner underscores the magnitude of U.S. economic power and the administration’s determination to bring it fully to bear on Iran.

As the shades of Robert McNamara and McGeorge Bundy can testify, however, great power does not automatically confer wisdom. Having demonstrated an impressive ability to squeeze Iran, North Korea and Venezuela, the Trump administration now needs to translate raw power into policy success. This goal remains elusive with all three countries so far, and the path forward is anything but clear.

Administration critics charge that the current Iran policy represents an attempt by inveterate hawks to plunge the U.S. into a war with the Islamic Republic. It would be more accurate to say that the administration counts on Iranian fear of conflict with the U.S. and its regional allies to curb Iranian provocations as sanctions bite. Until recently, this appeared to be working; Iran continued to comply with the terms of the nuclear deal negotiated by the Obama administration, and its activities in the region were no more nefarious than usual.

That seems to have changed. The recent attacks in the Gulf of Oman, together with Iran’s announcements that it will exceed the nuclear deal’s limits on its supply of enriched uranium this month—and accelerate its enrichment program in July—signal that Tehran is trying some brinkmanship of its own. Iranian authorities may believe that President Trump is constrained politically, and that for all his bellicose rhetoric he is deeply reluctant to involve the U.S. in another war in the Middle East.

Attacks on ships engaged in peaceful commerce in international waters are immoral and illegal and threaten the web of commerce on which the U.S. and its allies depend. But as long as no Americans are killed and no American-flagged carriers are struck, it will not be immediately clear to much of Mr. Trump’s base why the U.S. should retaliate militarily for attacks on Norwegian and Japanese ships—particularly since those nations are not clamoring for a response.

Moreover, many U.S. allies—alarmed at the nature of American Iran policy and appalled at their inability to influence the administration’s decision making—blame the White House rather than Tehran for the instability. If the situation escalates, U.S. allies might grow even less willing to confront Iran over its nuclear-deal violations.

As long as the flow of oil from the Middle East is essentially unaffected by pinprick attacks and Iran refrains from an all-out nuclear effort, there is a strong argument for military restraint in Washington. The status quo is weakening Iran and improving the American bargaining position. The U.S. cannot ignore Iranian provocations, but it also should not allow them to deflect it from a policy that is working. While taking all necessary action to keep traffic moving freely in international waters, the administration’s best option for now is to concentrate on tightening sanctions on Iran and its proxies.

The greatest danger is an Iranian miscalculation. Mr. Trump is not eager for war, but there are provocations that would ignite his Jacksonian base and make the pressure for war hard to resist. In the current atmosphere, any attack on U.S.-flagged ships or servicemen could force a strong military response.

Adding to the uncertainty is Tehran’s read of the political situation in the U.S. Iran’s leaders may overreach if they believe that Mr. Trump is a paper tiger or that the U.S. is too divided to strike back. Yet they also may hope they will get better terms if a Democrat defeats Mr. Trump in 2020. Why risk a devastating war now if relief is only 19 months away?

Despite the white-knuckle tension in and around the Persian Gulf, the potential for U.S.-Iranian peace may be higher now than in the past. The Trump administration’s willingness to tolerate and even enter partnerships with nondemocratic regimes like those in Egypt and Saudi Arabia suggests that a pragmatic relationship with a less revisionist Iran could be possible.

Tehran’s imperial ambitions—not ideological hostility in Washington—are at the root of this conflict. Iranian negotiators genuinely interested in a modus vivendi would get a hearing in Washington. That might seem unlikely now, but both countries and the region would benefit enormously from even a cold peace.