A day after the United States signed a landmark nuclear deal with Saudi Arabia, President Trump added a new condition to the sale of nuclear reactors to the kingdom, declaring that the entire arrangement now depends on the Saudi willingness to establish diplomatic relations with Israel.

The deal “will be approved, but is totally subject to Saudi Arabia joining the very respected and successful Abraham Accords,” Mr. Trump said in a post on his social media site, referring to a series of agreements that normalized relations between Israel and other states, including Bahrain and the United Arab Emirates.

There was no mention of any such condition in the administration’s announcement that the deal had been signed on Wednesday, but Mr. Trump’s social media post put the agreement’s immediate future in doubt. The Saudi government has made clear it has no intention of recognizing Israel without creating a pathway toward the creation of a Palestinian state. Mr. Trump never addressed that issue in his brief post.

In linking the deal to diplomatic recognition of Israel, Mr. Trump is veering back to the plan that President Joseph R. Biden Jr. attempted in the first years of his administration, making nuclear cooperation part of a larger diplomatic understanding that changes the dynamics of the Middle East. But the plan fell apart after the Oct. 7, 2023, terrorist attacks on Israel by Hamas, and Mr. Trump later divorced the nuclear agreement from the diplomatic effort.

He has now reversed himself, but only after his energy secretary, Chris Wright, signed the deal with Saudi Arabia’s energy minister. Mr. Wright indicated that the deal would now be sent to Congress for review, but presumably Mr. Trump could hold up its transmission while he argues with the Saudis over the new condition.

Not surprisingly, Prime Minister Benjamin Netanyahu of Israel warmly greeted Mr. Trump’s demand that the Saudis normalize relations with Israel. “The joint American and Israeli military action against the genocidal regime in Tehran and Israel’s crushing of Iran’s terror axis have created the possibility to expand the circle of peace,” he said in a statement. “As President Trump has said, Saudi Arabia’s joining of the Abraham Accords would be an historic leap forward for peace in the Middle East.”

Saudi Arabia’s Center for International Communication did not immediately respond to requests for comment on Mr. Trump’s demand.

Mr. Trump also asserted that the terms of the deal would not allow Saudi Arabia to enrich its own nuclear material, offering no further explanation. While the agreement has not been made public, officials have described it very differently, saying that it allows for a two-year study period, during which Saudi and American officials will determine if there is a viable economic path for the kingdom to enrich nuclear fuel. The United States could block that move for a number of years, according to officials familiar with the arrangement, but not permanently.

Mr. Trump argued otherwise.

“There will be no enrichment of material,” he stated, adding that the United States “is not opposed to Civil (Non-Enriched) Nuclear Facilities.”

The potential that Saudi Arabia could make its own fuel — and the risk that some of it could be diverted to a nuclear weapons project in the future — lies at the core of criticism of the deal. But the country’s de facto leader, Crown Prince Mohammed bin Salman, is unlikely to give up the right to enrich or agree to the most intrusive international inspections that more than 140 other nations have already signed.

Mr. Trump’s statement comes after Israeli leaders voiced concerns over the emerging deal, worrying that it could fuel a regional arms race, and the implication of Israel being sidestepped in the process.

But Mr. Trump’s newly stated condition could create a roadblock to the deal itself, as Saudi officials have repeatedly stated that they will not recognize Israel without a pathway toward a Palestinian state.

Mr. Trump has previously pushed to expand the Abraham Accords, agreements he began brokering during his first term. The first, between Israel and Bahrain and the Emirates, were announced in 2020. Since then, Morocco and Sudan have joined the pact.