Under the reported terms of the “123” agreement, which specifies legal terms for nuclear cooperation between the United States and foreign countries under Section 123 of the 1954 Atomic Energy Act, the U.S. would gain an edge in securing contracts to build Saudi Arabia’s nuclear sector, including reactors. However, that commercial opportunity appears linked to eventual American authorization of uranium enrichment in the kingdom. Washington and Riyadh would spend two years studying whether an American-built uranium enrichment plant on Saudi soil is economically viable.

Yet what sounds like due diligence is really a door left ajar: If the study concludes that enrichment is economically desirable, the restriction would lapse and centrifuges could operate on Saudi territory. Little would stop Riyadh from later nationalizing the enrichment plant, as it did with the American-owned Arabian-American Oil Company in 1980 — forcing a future American president to consider military action to stop the Saudis from using the plant as a source of nuclear weapons fuel.

Absent a strict “black-box” restriction preventing Saudi scientists from working at the facility, Riyadh could also acquire the knowledge needed to build a covert enrichment plant of its own, exactly as A.Q. Khan did while working at the Dutch Urenco facility — part of a European enrichment consortium — in the 1970s. Khan learned centrifuge technology, stole blueprints, and enabled Pakistan’s uranium pathway to nuclear weapons, along with those of Libya, Iran, and North Korea.

Worse, the reported 123 agreement would not bind Riyadh to the International Atomic Energy Agency’s enhanced inspections agreement known as the Additional Protocol, denying U.N. inspectors the short-notice access to undeclared sites required to detect covert activity. The administration claims a bilateral inspection agreement can close this gap, yet it is doubtful such an arrangement would grant American access to every site of concern. Once Saudi Arabia possesses the means to produce nuclear weapons fuel via uranium enrichment, Riyadh could more easily conceal subsequent steps toward weaponizing it. Thus, any deal without the Additional Protocol amounts to tacit U.S. acceptance that Riyadh prefers the world to be blind to its activities.

This is not an isolated policy. Last year, Washington authorized future enrichment and reprocessing for South Korea, abandoning decades of bipartisan resistance to spreading fuel-cycle technology. By contrast, the United Arab Emirates accepted a binding “gold standard” ban on enrichment and reprocessing in its 2009 nuclear agreement with Washington and has built a peaceful program.

That is the precedent to reinforce, especially given Riyadh’s past statements that it will acquire nuclear weapons if Iran does, and Washington’s elimination of Iranian enrichment and simultaneous demand that Tehran abandon the activity for good.

With a Saudi precedent set, Turkey, Egypt, and possibly Qatar, Oman, and even the UAE would likely press similar requests for U.S.-built enrichment plants on their soil. If refused, they may pursue enrichment or reprocessing independently.

Saudi officials warn that if Washington refuses enrichment, Riyadh will turn to China, Russia, or even Pakistan. That threat is no reason to acquiesce. Washington should remind Riyadh of the advanced U.S. defense systems, military assistance, and security partnership against Iran — benefits keenly demonstrated over the past year during the conflict with the Islamic Republic — that the Saudis would put at risk. At the same time, the U.S. can offer competitive reactor deals and non-enrichment fuel-cycle assistance while insisting that enrichment and reactor fuel fabrication remain on U.S. soil.

If Saudi Arabia is determined to acquire proliferation-relevant capabilities, the wiser course is to constrain that ambition — not hand over the technology that enables a weapon.

Accordingly, Republican leaders should insist the president renegotiate the deal to secure the Additional Protocol and an unconditional ban on enrichment and reprocessing. Should the administration refuse, Congress should use its 30-day consultation period to advance a joint resolution of disapproval and, if necessary, override a presidential veto during the remaining 60 days.

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A veto-proof two-thirds majority in both chambers would be required — difficult to achieve if the president remains committed to the current terms. Some Republican senators have voiced consternation with the agreement, but it’s unlikely a sizable portion of Republicans in the House and Senate would oppose the president. Democrats have also introduced legislation demanding sound terms, but those bills would face the same veto hurdle.

In the end, Trump will have the final say. He is well acquainted with the dangers of enrichment in Iran. And notwithstanding the terms of the Riyadh deal, his rhetoric suggests he is against Saudi enrichment. It is time he convey that judgment clearly and insist on a better deal.

Andrea Stricker is deputy director of the nonproliferation program and a research fellow at the Foundation for Defense of Democracies. Tyler Stapleton is senior director of government relations at FDD Action.