The E.U. says it will impose new sanctions on Iran’s drone and missile programs.

The president of the European Council announced early Thursday that new European sanctions would be imposed on Iran’s drone and missile programs as punishment for last weekend’s attack on Israel.

“It’s a clear signal that we want to send,” the president, Charles Michel, said, emerging after midnight from a meeting of leaders of the European Union’s member states in Brussels. “We need to isolate Iran.”

He said more details about the new sanctions would be announced in the coming days. But it was far from clear how new restrictions would curb Iran, which has spent decades finding ways to skirt Western sanctions, including illicit shipments of oil and, notably, its armaments to Russia.

Mr. Michel’s comments came hours after the top diplomats from Britain and Germany visited Israel to urge Prime Minister Benjamin Netanyahu not to risk igniting a wider war by responding too strongly to Iran’s barrage of missiles and drones last weekend.

Despite their efforts, Mr. Netanyahu emerged from talks resolute that his country would not bow to any outside pressure when choosing its response. He declared before a cabinet meeting that Israel would “do everything necessary to defend itself,” and warned his allies, most of which are pushing him to exercise caution, that “we will make our own decisions.”

“It is clear that the Israelis are making a decision to act,” Britain’s foreign secretary, David Cameron, told the BBC before meeting with Mr. Netanyahu. “We hope that they do so in a way that does as little to escalate this as possible.”