PARIS — A U.S. ambassador in Europe was recently asked by an Israeli ambassador what could be done to improve the lousy relations between Prime Minister Benjamin Netanyahu and President Obama. He replied: “Every once in a while, say thank you.”

The American ambassador added a couple of other thoughts. “Maybe, once in a while, ask the president if there’s anything you can do for him. And above all stay out of our election-year politics.”

This sharp riposte reflects Obama’s fury at several things: the way Netanyahu has gone over his head to a Republican-dominated Congress where he is a darling; Netanyahu’s ingratitude for solid U.S. support, including the veto of an anti-settlements resolution at the United Nations last year and opposition to the unilateral Palestinian pursuit of statehood; the delaying tactics of Netanyahu reflecting his conviction Obama is likely a one-term president; and Netanyahu’s refusal to pause a second time in settlement building for the sake of peace negotiations.

I would add a further piece of advice to Netanyahu if he cares about his dysfunctional relationship with Obama — and he should because Israelis know the United States matters and might be disinclined to re-elect a man who has poisoned relations with Washington. That advice is: Do not attack Iran this spring or summer.

Netanyahu is tempted to bomb Iran in the next several months to set back its opaque nuclear program and — despite a call from Obama last Thursday and messages from Defense Secretary Leon Panetta — has declined to reassure the United States that he will not. Several factors, Iranian and American, incline Netanyahu to move soon.

The first is the Israeli judgment that Iran is close to “irreversibility” in its pursuit of the various elements — from uranium enrichment to trigger mechanisms — needed for a nuclear warhead. The start of enrichment at the Fordow underground facility near Qum intensified these concerns, as has Iran’s bellicose tone in response to threatened oil sanctions.

Then there is the American political calculus. An Israeli strike a few months before the U.S. election in November would stymie Obama. He would be in no position to express anger given the clout of the pro-Israel lobby, the important Jewish vote in Florida and the fulsome support any Israeli bombing would get from the Republican contender — probably Mitt Romney.

By contrast, a re-elected Obama would, as a second-term president, have room to mark his displeasure if Israel was to go it alone. Because awareness is growing that Obama could indeed win, these considerations carry weight in Jerusalem.

Netanyahu has always portrayed himself as the man standing between Iran and a bomb. A hawk, he has a taste for the dramatic. Israel, in such issues, has already gone it alone once, when it bombed a Syrian nuclear facility in 2007. At this stage, the U.S. and Israeli triggers appear distinct — with Panetta saying “our red line to Iran is, do not develop a nuclear weapon” whereas the Israelis see irreversible nuclear capability as unacceptable even if a weapon is not being made. In that discrepancy lurks danger.

Don’t go there, Mr. Netanyahu. It would be a terrible mistake. Choosing between the United States and Iran is a no-brainer. One is a great power and essential friend. The other is a blustering, combustible society that’s been tinkering with a nuclear program for decades and whose closest regional ally, Syria, is on the brink.

Israel’s dream is that the United States will do the bombing for or in conjunction with it — one reason for the Israeli refusal to clarify its intentions. But, short of an outrageous Iranian provocation such as blocking the Strait of Hormuz, that’s not going to happen before November.

In an election year, with U.S. intelligence convinced Iran is not yet building a bomb, Obama will not send oil prices soaring and the Muslim world into another bout of anti-American rage. A lot of his presidency has been precisely about extraction from war and easing of Islamic hostility.

Netanyahu did say this past weekend that “for the first time” he saw some “wobble” in Iran as a result of sanctions. But he also called for “a clear statement” that the U.S. would “act militarily” if sanctions fail. Meanwhile, in a good-cop-bad-cop routine, his vice prime minister was grumbling that U.S. sanctions had been disappointing.

Here’s the bottom line: an Israeli attack unites Iran in fury, locks in the Islamic Republic for a generation, cements the Syrian regime, radicalizes the Arab world at a moment of delicate transition, ignites Hezbollah on the Lebanese border, boosts Hamas, endangers U.S. troops in the region, sparks terrorism, propels oil skyward, triggers a possible regional war, offers a lifeline to Iran just as Europe is about to stop buying its oil, adds a Persian to the Arab vendetta against Israel, and may at best set back Iran’s nuclear ambitions a couple of years.

Sound promising?

Gen. Martin Dempsey, the chairman of the U.S. Joint Chiefs of Staff, will visit Israel soon. Netanyahu should listen, take his finger off the Iranian trigger — and realize Israel’s fate hinges more on Ramallah than Tehran.