IF ISRAELI Prime Minister Benjamin Netanyahu hoped that President Obama would publicly spell out the conditions under which the United States would attack Iran’s nuclear facilities, he likely was disappointed by Monday’s meeting at the White House. Though he spoke expansively about the threat an Iranian nuclear weapon would pose to U.S. national security, Mr. Obama did not advance beyond his long-held position that “all options are at the table.”

By the same token, if Mr. Obama hoped that the Israeli leader would endorse his assertions that “the prime minister and I prefer to resolve this diplomatically” and “do believe that there is still a window that allows for a diplomatic resolution,” he was not satisfied. Mr. Netanyahu made no reference to diplomacy; instead, he underlined that “Israel must reserve the right to defend itself,” adding, “My supreme responsibility . . . is to ensure that Israel remains the master of its fate.”

Though each man spoke of the solidity of the countries’ alliance, there is little doubt that Mr. Obama and Mr. Netanyahu continue to assess the threat from Iran and the best means of addressing it differently. Whether that leads to an Israeli strike on Iran over U.S. objections, Mr. Obama was no doubt right to predict “a series of difficult months” ahead.

In our view, Mr. Obama’s arguments against an early attack on Iran, which he outlined in a speech to the AIPAC (American Israel Public Affairs Committee) lobbying group and in an interview, as well as alongside Mr. Netanyahu, were persuasive. Mr. Obama conceded that Iran had not yet made a decision to seek a diplomatic settlement with the West. But he told the Atlantic’s Jeffrey Goldberg that Tehran “is not yet in a position to obtain a nuclear weapon without us having a pretty long lead time in which we know that they are making that attempt.”

While not explicitly threatening military action in that instance, Mr. Obama was clear in saying that “my policy . . . is not going to be one of containment,” and that preventing Iran from obtaining a bomb was “profoundly in the United States’ interest.” That should undercut charges by GOP presidential candidates that the president is ready to accept an Iranian bomb.

The gap this leaves in U.S.-Israeli relations is nevertheless twofold. First, Mr. Netanyahu’s government contends that Iran must be stopped not just from building a bomb but also from acquiring the capacity to do so. Second, Israel is reluctant to allow Iran to pass into a “zone of immunity” in which key nuclear facilities might be invulnerable to Israeli attack. Though the United States would retain the capacity to act, Mr. Netanyahu may not countenance a situation in which Israel is not “master of its fate.”

It’s also possible — even likely — that, having established the principle that Israel is prepared to act unilaterally, Mr. Netanyahu and his government will choose not to do so. That would give the United States and its allies an opportunity to probe Iran’s willingness to make concessions in another round of negotiations, which are expected this spring. Otherwise, Mr. Obama’s pledge that “the United States will always have Israel’s back when it comes to Israel’s security” will be put to the test.