JERUSALEM — To Prime Minister Benjamin Netanyahu, it’s a “historic opportunity”: the chance to annex large stretches of the occupied West Bank that right-wing Israelis have long coveted, possibly giving the country a permanent eastern border for the first time.
Annexation would also cement his place in history, carving out a permanent legacy for Israel’s longest-serving leader. And although he has not disclosed the scope of his plan, he has promised to move forward with it as soon as July 1.
But as that date nears, a growing chorus of respected former Israeli military, intelligence and diplomatic officials is denouncing any unilateral annexation as a grave risk to Israel’s security.
Imposing Israeli sovereignty on territory the Palestinians have counted on for a future state could ignite a new uprising on the West Bank, these experts warn. Neighboring Jordan could be destabilized. Israel’s move would be broadly denounced as illegal, potentially leading to international isolation.
And the resulting furor, they say, could distract from efforts to intensify pressure on the country Mr. Netanyahu has long portrayed as the greatest threat facing Israel and the world: Iran.
“In the military, you learn at the lowest level to focus on the main effort,” said Amos Gilead, a retired major general in military intelligence who was also an envoy to the Arab world. “To be united with the Arabs against Iran is an unbelievable advantage,” he said. Instead, he said, “We will unite the whole world against us.”
Already, Arab leaders have warned that annexation would threaten Israel’s progress in forging ties with their countries, in part over their common adversary in Tehran — progress that Mr. Netanyahu has brandished as proof of his statesmanship.
The Trump administration supports annexation in principle, and several Americans, including Ambassador David Friedman, are part of the joint Israeli-American committee that is working in secret to map Israel’s new borders.
But annexation is fueling consternation among Democrats in Congress and is opposed by the party’s presumptive presidential nominee, Joseph R. Biden Jr., all of whom favor a negotiated solution to the Israeli-Palestinian conflict.
Mr. Netanyahu has not responded publicly to the criticism, saying recently, “The less I say about this now, the greater our chances of achieving the best result.”
And the few officials in a position to explain and defend his thinking have refused to do so publicly. His office refused to comment for this article, as did Ron Dermer, Israel’s ambassador in Washington and a key figure in the annexation push.
Mr. Netanyahu promised last fall to annex the strategically important Jordan Valley, a move that would create an eastern border abutting Jordan. In January, he said he would annex even more: about 30 percent of the West Bank, including dozens of existing Jewish settlements, in keeping with a conceptual map in the Trump administration’s peace plan.
But the administration has since called upon Mr. Netanyahu to reach a consensus with his centrist coalition partner, Defense Minister Benny Gantz, who has opposed unilateral moves. Their private talks have produced trial balloons — from a modest, largely symbolic annexation to taking the whole 30 percent, or moving in phases — but little clarity.
The Palestinians have rejected any unilateral move as a violation of Israel’s commitments to mutually negotiated borders under the Oslo accords. They have withdrawn from the agreement and the Palestinian Authority, which governs the West Bank, has suspended security cooperation with Israel in protest.
The fear most unnerving Israelis is that their sons and daughters could be sent into combat. If the Palestinian Authority collapses or Palestinians respond with an uprising, Israel could be forced to militarily reoccupy a restive West Bank.
“Look us in the eyes,” demands a new ad campaign by a prominent group of opponents, Commanders for Israel’s Security, over a photo of a young Israeli infantryman. “Admit that you have no idea how unilateral annexation will end.”
Backers of annexation downplay the odds of a resurgence of violence on the West Bank, noting that similar predictions after President Trump’s recognition of Jerusalem as Israel’s capital and his decision to move the American embassy there from Tel Aviv never materialized.
But security experts say that annexation would be far more provocative, tantamount to saying that the state that Palestinians thought they were building was no longer in the cards.
“The moment there is unilateral annexation, the Palestinian Authority will lose its legitimacy,” Mr. Gilead said. “If they do, sooner or later they will not be able to show their faces in the Palestinian street. And who will pay the price? Our soldiers.”
Israeli taxpayers could pay, too: Resuming a full-blown military occupation would cost billions, experts say. In addition to ending security cooperation, Palestinian officials started the financial equivalent of a hunger strike to show they are willing to let the authority collapse if Israel annexes territory.
Yossi Kuperwasser, a retired general in military intelligence who is among the most outspoken supporters of annexation, dismissed the idea that Israel would have to take full control even in Palestinian cities.
“It’s nonsense,” he said. “We are not going to annex Nablus. The Palestinians will take care of themselves.”
But relegating the Palestinians to self-government in confined areas — places Israeli critics have likened to “bantustans” — could close the door to a viable state, forcing Israel to choose between granting Palestinians citizenship and leaving them in an apartheidlike second-class status indefinitely.
“If we take steps that make separation from the Palestinians impossible, we may undermine or destroy the very root of the entire Zionist enterprise,” said Sallai Meridor, a former Israeli ambassador to the United States.
Repercussions could be felt in Jordan, a key security partner for Israel, where a majority of the population has Palestinian roots.
The Palestinian majority will put pressure on King Abdullah II to take bold action against Israel in response to any annexation, experts say. And annexation would reinforce fears in Jordan that the Palestinians, denied a state on the West Bank, would try to make Jordan their new homeland instead.
Israeli analysts say he could close Jordan’s embassy in Israel, possibly scrap a new deal to import natural gas from Israel, or even curtail security cooperation that includes intelligence sharing and allowing overflights by Israeli jets attacking Iranian targets in Syria.
Mr. Kuperwasser discounted the impact of any Jordanian reaction.
“There are limits in how far they can go,” he said, speculating that the kingdom’s heavy dependence on aid from Washington would limit its response.
Mr. Netanyahu has wowed Israelis by making diplomatic inroads in the Arab and Muslim worlds. He has crusaded against Iran’s nuclear project and its ambitions in Syria, Lebanon and Iraq. And he has relegated the Israeli-Palestinian conflict to the international back burner.
But annexation could undo much of that diplomatic progress in an instant, critics warn.
A senior United Arab Emirates diplomat warned Israelis that annexation would reverse Israel’s efforts to forge deeper ties with his country and the wider Arab world. A host of countries have issued statements opposing annexation, and the German foreign minister flew to Jerusalem last week to urge Israel to stand down.
The European Union’s foreign policy chief, Josep Borrell, said Thursday that annexation “would inevitably have significant consequences” for the bloc’s relationship with Israel.
Mr. Meridor, the former ambassador, warned in the Israeli newspaper Yediot Ahronot of damage to Israel’s ties “with the overwhelming majority of the world’s countries,” adding: “True, the relationship with President Trump is important and good, but should we put all our eggs in one basket?”
At a minimum, he said in an interview, annexation would pose an immediate problem for Israel’s envoys by depriving them of their strongest response to questions about the protracted subjugation of Palestinians.
“This was the easiest and most compelling answer that any Israeli diplomat could give throughout the years,” he said. “‘We’re willing to negotiate, to compromise, but the other side turned us down.’ That’s an asset we’ve had. And we may lose it if we annex unilaterally.”
To Mr. Kuperwasser, the goal is not just to expand Israel’s territory but to show the Palestinians that they will lose something for refusing to engage with Israel on the basis of the Trump administration’s plan.
“Before, we needed the consent of the Palestinians for any move,” he said. “This new paradigm says, from now on, you don’t have veto power.”
Mr. Kuperwasser said annexing the Jordan Valley was the best way to drive that point home, because the Palestinians want it as a gateway to the Arab world, while Israelis consider controlling it nonnegotiable for security reasons.
He acknowledged some of the diplomatic risks and expressed hope that they could be mitigated beforehand. But he said it was more important not to miss a “golden opportunity” that could evaporate with a Trump defeat in November.
Even an opponent of annexation, Oded Eran, a former Israeli ambassador to Jordan, acknowledged what he called a rare “alignment of the stars” in favor of it: a president with a “messianic mission” to support Israel, and the pandemic and economic turmoil diverting regional attention to local matters rather than geopolitics.
“It’s a Rolls-Royce, but the price fell by half,” Mr. Eran said. “It’s red, electric, and you have to recharge it only once a week. Who wouldn’t want that deal?”