By Felicia Schwartz

TEL AVIV -- Talks between the U.S. and the United Arab Emirates on a potential sale of advanced F-35 jets is raising thorny questions for Israel's security in the Middle East.

The U.A.E. has long sought the jet fighters, and the deal last week to normalize diplomatic relations with Israel was forged with an understanding that the Emiratis could have access to more advanced American military hardware, according to U.S. officials. Up until recently, Washington had rebuffed the requests for advanced jet fighters because of the shared policy of ensuring Israel maintained a qualitative military edge in a region where it has many enemies. President Trump said Wednesday that talks on the sales are under way.

Any change now in Israel's capacity to acquire the latest military equipment -- and deprive it from potential rivals -- risks tipping the balance of power in the region, analysts warn. "It's not just a real time issue, it also enhances Israel's deterrent capacity," said Aaron David Miller, a former adviser to Democratic and Republican secretaries of state now at the Carnegie Endowment for International Peace.

The F-35s, advanced fifth generation stealth fighters that can't be seen by most enemies, are particularly sensitive. Israel has purchased about 50 of the jets, including 20 that have arrived so far, and used them in Syria to carry out strikes as part of its campaign to erode Tehran's military foothold in Syria.

Since Israel and the U.S. agreed on maintaining Israel's superiority, nearby and neighboring countries have received advanced jets like F-15s and F-16s, but only years after Israel already had them.

The U.A.E. reached a diplomatic breakthrough with Israel, brokered by the Trump administration, in part because the Gulf Arab nation shares a hostility to Iran. American and Israeli officials say such a sale isn't explicitly part of the agreement, though the Emiratis say it sets the stage for it.

"The U.A.E. expects its requests will be accepted," Anwar Gargash, U.A.E. Minister of State for Foreign Affairs, said at an event hosted by the Atlantic Council think tank. "And we feel that with the signing of the peace treaty [with Israel]...any hurdles should now longer be there."

Iran has hundreds of short- and medium-range ballistic missiles, which it sees as a way to compensate for the limitations of its air force, experts say. Iran's air fleet has been hobbled by decades of sanctions, putting it at a disadvantage to regional rivals with more advanced air power, including Israel, Saudi Arabia and the U.A.E.

On Wednesday, President Trump told reporters that the Emirati interest in buying the jets was under review and linked it to the recent U.S.-backed accord. "They would like to order quite a few F-35s," he said.

While Israel and the U.A.E. share common interests against rival Iran for now, Israeli officials worry about losing the country's military advantage in the region over the long term. Any sale to the U.A.E. could take five to eight years to complete and a future presidential administration could block it, officials and analysts said.

That the diplomatic deal with the U.A.E. possibly came with implicit Israeli approval for the transfer of advanced American military hardware to the Arab nation has elicited fierce criticism from Israeli Prime Minister Benjamin Netanyahu's own coalition partners.

"It is forbidden to take risks with security," Benny Gantz, the defense minister and also a former Israeli military chief, told reporters on Tuesday. He said Mr. Netanyahu only informed him about the deal with the U.A.E. after it was reached.

The possible sales also sparked criticism from Israel's security establishment.

"Israel must never forget, not even for an split second, that any dent in its strength is liable to pull the rug out from under its feet in the long term," Amos Gilad, former head of the Defense Ministry's political-military affairs bureau, wrote in leading daily Yedioth Ahronoth on Thursday. "It is imperative that Israel prevent the sale of F-35 planes to any country in the Middle East and that it reserves its capabilities and similar ones for itself."

Officials said the F-35 gives Israel clear superiority in the region, and that while the U.A.E. is friendly now, that could change. They point to Turkey, which had planned to buy 116 Lockheed Martin Corp.-made F-35 fighters but was formally ejected from the program last summer after Ankara decided to purchase a Russian air-defense system.

"Turkey is a cautionary tale," said Mark Dubowitz, chief executive of the Foundation for Defense of Democracies, a Washington think tank. It shows "what happens when you commit to sell F-35s to an ally which years later under a different government becomes hostile to the U.S. and Israel."

--Stephen Kalin in Riyadh and Warren Strobel in Washington, D.C. contributed to this article.

Write to Felicia Schwartz at Felicia.Schwartz@wsj.com