Israel’s caretaker prime minister, Yair Lapid, pushed President Biden on Thursday to go beyond his public commitment to stopping Iran from ever obtaining a nuclear weapon, declaring that all democratic nations must vow to act if the Iranians continue “to develop their nuclear program.”

The distinction between Mr. Biden’s commitment and Mr. Lapid’s declaration was more than semantic: It goes to the heart of their countries’ differing approaches in dealing with Iran’s nuclear ambitions. Israel has conducted a series of covert sabotage and assassination operations to slow Iran’s ability to enrich nuclear fuel, while Mr. Biden has insisted that diplomacy, and a restoration of the 2015 Iran nuclear agreement, are the best way to find a permanent solution.

“If they continue to develop their nuclear program, the free world will use force,” Mr. Lapid said at the opening of a news conference in Jerusalem after the two leaders met as part of Mr. Biden’s four-day visit to the Middle East. During those remarks, Mr. Biden listened attentively but never repeated that commitment. Instead, he stuck to talking about blocking Iran from obtaining a weapon — not a program that might be intended to develop one.