President Donald Trump announced Thursday that a newly reached agreement with Saudi Arabia for a civilian nuclear program will be contingent on the kingdom normalizing relations with Israel through the Abraham Accords, significantly altering the terms of the deal via social media.

In a post on social media, the Republican president stated that the deal does not allow for uranium enrichment. However, nonproliferation experts have expressed concerns that the agreement lacks guardrails to prevent enrichment of uranium to weapons-grade levels.

"Will be approved, but is totally subject to Saudi Arabia joining the very respected and successful Abraham Accords," Trump wrote. He added that the U.S. "is not opposed to Civil (Non-Enriched) Nuclear Facilities."

The Saudi Embassy in Washington declined to comment Thursday on Trump's assertion that the deal requires the kingdom to join the accords. The Saudis have previously made clear that normalizing relations with Israel would first require the establishment of a clear path for Palestinian statehood. Israeli Prime Minister Benjamin Netanyahu has rejected the idea of Palestinian statehood, calling it untenable for Israel's security.

Netanyahu's office issued a statement applauding the prospect of Saudi Arabia joining the accords as a "historic leap forward for peace in the Middle East," though the statement made no mention of the deal to bolster Saudi Arabia's civil nuclear program.

Saudi Arabia is the most significant Arab power in the Middle East, and Trump considers the kingdom's participation in the accords critical to long-term regional stability. The 2020 agreements — originally signed by the United Arab Emirates and Bahrain, and later joined by Sudan and Morocco — expanded the number of Arab and Muslim-majority nations with diplomatic ties to Israel and also formalized commercial ties between Israel and several of those nations.

Details of the Nuclear Agreement

The nuclear deal, announced Wednesday, is expected to span 30 years and involve U.S. firms in the program's development. According to a person familiar with the matter who was not authorized to comment publicly, it could allow for the construction of a uranium-enrichment facility in Saudi Arabia following a joint U.S.-Saudi study.

The agreement does not include the International Atomic Energy Agency's "additional protocol," which would permit additional monitoring, inspections, and verification, according to a second person familiar with the decision. The agreement is to be submitted to Congress for review, according to both the U.S. and Saudi governments.

The White House and Saudi Arabia have not made public the text of the nuclear cooperation agreement, known as a "123 agreement" — so named for Section 123 of the U.S. Atomic Energy Act of 1954, which sets the conditions for significant nuclear cooperation between the United States and other nations — or what the Trump administration described as a "bilateral safeguards agreement" signed Wednesday by U.S. Energy Secretary Chris Wright and Saudi Minister of Energy Abdulaziz bin Salman.

Saudi Arabia's Energy Ministry said Wednesday that the agreement bolsters "efforts to diversify energy sources, advance cutting-edge technologies, and expand opportunities for cooperation and investment in ways that serve the mutual interests of the two friendly countries."

Proliferation Concerns and Regional Context

While uranium enrichment is not an automatic path to a nuclear weapon — a nation must also master other steps, including the use of synchronized high explosives — it does open the door to weaponization, which has fueled international concerns over Iran's nuclear program. Crown Prince Mohammed bin Salman stated publicly in 2018 that if Iran developed a nuclear weapon, Saudi Arabia would follow suit "without delay," underscoring the regional stakes riding on the terms of any civilian nuclear agreement with Riyadh.

Secretary of State Marco Rubio told reporters Thursday in Manila that the agreement would ensure Saudi Arabia works with American companies rather than "competitors" on its civil nuclear program. China, South Korea, France, and Russia are among alternative partners Riyadh could pursue.

"We're not the only show in town, but we're the best show in town," Rubio said. "We want to make sure that it's our companies they're picking."

Political Headwinds

The aftermath of Israel's war in Gaza and the nearly five-month-old U.S. and Israel war against Iran have complicated Trump's push to expand the accords. The agreements have drawn public opposition in certain signatory countries such as Morocco and Bahrain, sparking widespread protests.

Despite these challenges, the Trump administration remains optimistic that an agreement with Saudi Arabia on joining the accords can be secured by the end of Trump's second term.

As details of the deal emerged Wednesday, opposition on Capitol Hill and elsewhere began to mount, with Republicans and Democrats alike questioning the agreement. Conservative commentators who have generally supported Trump's policies asked why the president would provide Saudi Arabia such a deal without concessions in return. Trump then abruptly announced Thursday that the deal is entirely contingent on Saudi Arabia joining the accords.

The United Arab Emirates, Saudi Arabia's neighbor, signed a 123 agreement with the U.S. to build its Barakah nuclear power plant with South Korean assistance. The UAE did so without seeking enrichment — a stance nonproliferation experts have cited as the "gold standard" for nations pursuing atomic power.

Congressional Scrutiny

Rubio, as a Republican senator representing Florida, backed a bipartisan 2018 proposal that called for requiring Congress to approve any 123 agreement with Saudi Arabia. The bill was reintroduced by a group of Democratic lawmakers in March but has not passed into law.

Rep. Brad Sherman, a California Democrat, cosponsored the 2018 bill with Rubio that would have required congressional approval for a nuclear agreement with Saudi Arabia. He said he "misses Sen. Rubio," arguing that Secretary Rubio now appears to hold a different position.

"I hope that Sen. Rubio will return to us and insist that Congress approve any agreement," Sherman said Wednesday at a meeting of the House Foreign Affairs Committee.

Price reported from Manila, Philippines. Associated Press writers Sam Metz in Jerusalem and Matthew Daly and Matthew Lee in Washington contributed to this report.

This story was originally featured on Fortune.com.