WASHINGTON (AP) — Once-unthinkable coordination between Israeli and Arab militaries is in the spotlight as Joe Biden makes his first Middle East trip as president, heightening debates over whether the U.S.-backed initiative between former enemies strengthens defenses against Iran or makes a regional war more likely.

Israeli-Arab security overtures have multiplied since the 2020 Abraham Accords negotiated under the Trump administration normalized relations between Israel and four Arab League nations. They have have grown further since the Pentagon switched coordination with Israel from U.S. European Command to Central Command, or CENTCOM, last year. The move grouped Israel's military with former Arab opponents, including Saudi Arabia and other nations that have yet to recognize Israel.

Encouraging Arab nations to strengthen security ties and overall relations with Israel is one of the aims of Biden's travels to Israel and Saudi Arabia next week, National Security Council spokesman John Kirby said Thursday.

Already this year, robed Gulf Arab princes and other dignitaries watched from the deck of a warship as the U.S. launched training that had Israeli frogmen, sailors and defense technology splashing through the Red Sea in one of the increasing Israeli exercises alongside U.S. and Arab militaries.

An Israeli liaison officer is set to be assigned to U.S. Fifth Fleet headquarters in Bahrain, a Gulf nation that recognized Israel only in 2020. Arab and Israeli defense officials increasingly consult around the region, exploring areas for security coordination and how to align the expertise, intelligence and weapons to implement it.

Republican and Democratic lawmakers introduced legislation last month that would direct the Pentagon to shape a joint air defense system for Israel and Arab nations against Iranian ballistic missiles and drones.

Kirby said Thursday the U.S. is stressing coordination of regional air defense systems as an early step in the alliance "so there really is effective coverage to deal with Iran," Kirby said.

CENTCOM members also are working together on maritime security, an Israeli official said, speaking on condition of anonymity to discuss the still largely behind-the-scenes Arab and Israeli security consultations. The idea is that CENTCOM can coordinate among these nations and "realize that vision of having regional defense," the Israeli official said.

Biden has defended his upcoming meeting with Saudi rulers he had once shunned because of human rights abuses by saying he is acting partly at Israel's request.

The Arab-Israeli security coordination is deepening frustrations of Palestinians, who already feel they were sold out by the Abraham Accords, which did nothing to end Israeli occupation.

American officials until now have given few details of the the budding Israeli-Arab cooperation, mindful that Arab publics may oppose embracing a longtime enemy. The Pentagon declined a request for comment on this story. The Saudi embassy in Washington did not immediately respond to requests for comment.

For Arab and Israeli leaders, "the No. 1 motivator is the common threat they both perceive from Iran and Iranian proxies," said Daniel Shapiro, a former ambassador to Israel and a prominent advocate of the emerging coalition between Israel and individual Arab nations.

Especially to the extent Saudi Arabia comes on board, the security ties under CENTCOM raise prospects of a "truly unified Sunni Arab coalition to stand with Israel" against Shiite-led Iran, Shapiro said.

Israel considers Iran its greatest enemy, citing its nuclear program, military activities and support for hostile militant groups.

Gulf Arab states allied to the U.S. long have been wary of Iran's support of militias and proxies. While lacking American-made sophisticated weaponry, Iran has an unmatched arsenal of ballistic missiles, drones and other arms.

Promoting greater regional integration with Israel's modern military could soothe Saudi and Emirati complaints the U.S. is not doing enough to protect them from Iran. It potentially accustoms Arab nations to working with Israel, despite Israel's failure to reach the kind of political resolution with the Palestinians that Arab nations long demanded as a condition for recognizing Israel.

The U.S. also hopes the coordination will mean that regional actors will take more responsibility for their own security, allowing the U.S. to ease its decades-long safeguarding of Arab oilfields and turn more attention to Russia and China.

And in the short term of U.S. elections, the effort helps the White House emphasize the security aspect of a potentially humbling presidential trip that's intended partly to appeal to Saudi Arabia and other Arab countries for more oil, with no guarantee of success.

Opponents accuse Israel of exaggerating the Iranian threat.

"They want to get recognition from Arab states," said Vali Nasr, an Iran and Middle East expert at the Johns Hopkins School of Advanced International Studies, and a former adviser to the Obama administration. "And Iran is their ticket to that."

Nasr said the risks include igniting Middle East hostility by uniting and enabling the most hawkish enemies of Iran, including Israel and the United Arab Emirates, and by allowing the deep grievances underlying Israeli-Palestinian hostility to fester.

The coordination "looks like the U.S. is handing off security to Israel in order to focus on Ukraine and China," Nasr said. He said this could backfire by inflaming regional tensions that draw the United States back in.

Even stronger warnings came from now-Secretary of State Antony Blinken, in a 2017 article against President Donald Trump's promotion of an "Arab NATO." A Sunni Arab security alliance "could potentially pull the United States into the sectarian struggle between Sunni and Shia," Blinken wrote then.

The current initiative under CENTCOM is no Arab NATO, and instead promotes coordination among Israel and Arab partners to counteract threats from Iran, a U.S. official said, speaking under condition of anonymity to discuss the security alliance.

An open working relationship with Saudi Arabia would be a big prize for Israel in its increasing regional integration. Saudi Arabia has been most reticent publicly about any cooperation with Israel. Observers and advocates on all sides of the security partnerships said they expect no big breakthroughs during Biden's trip, although it is unclear whether the parties were trying to play down expectations.

Top Saudi officials have signaled their support for CENTCOM drawing Israeli's powerful modern military into the fold with Arab nations. Visiting the United States this spring, Deputy Defense Minister Khalid bin Salman made a point of visiting CENTCOM headquarters in Florida, inquiring about coordinating regional air defense capabilities and other steps.

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Federman contributed from Jerusalem. Lolita C. Baldor contributed from Washington.