President Trump has approved an agreement with Saudi Arabia to partner on developing the Kingdom’s civil nuclear energy program, according to two U.S. officials.

The deal leaves open the possibility that Saudi Arabia will enrich uranium domestically in the future, the officials said, a prospect that could raise concerns about nuclear weapons proliferation.

In the deal, the United States and Saudi Arabia have agreed to safeguards to inhibit any weaponization effort, the sources said. But that framework would be governed by the two countries themselves, instead of the International Atomic Energy Agency (IAEA), which conventionally oversees nuclear pacts.

Secretary of State Marco Rubio was asked about the agreement on Wednesday. He declined to comment on the contours of the plan but said that the Trump administration would work with Congress to formalize the deal.

“Suffice it to say, the U.S. is not going to reach any agreement with any country in the world that leads to the risk of proliferation,” Rubio said.

The agreement, under which U.S. industry would help develop Iranian nuclear infrastructure, spans 30 years and is valued at tens of billions of dollars, the officials said.

The U.S. and Saudi Arabia discussed details of the proposal during a visit to Washington, D.C. by Saudi Crown Prince Mohammed bin Salman last fall. The administration is expected to submit the deal to Congress, which is required by federal law.

The Wall Street Journal first reported that the president had approved the deal.