Former President Donald J. Trump spoke recently with Saudi Arabia’s de facto ruler, Prince Mohammed bin Salman, their first publicly disclosed conversation since Mr. Trump left office in January 2021, according to two people briefed on the discussion who were not authorized to speak publicly about it.

It was unclear what the two men discussed and whether it was their only conversation since Mr. Trump’s departure from the White House. Neither representatives for Mr. Trump nor an official of the Saudi government responded to requests for comment.

But news of their discussion comes at a time when the Biden administration is engaged in delicate negotiations with the Saudis aimed at establishing a lasting peace in the Middle East, building on diplomatic ties between Israel and a number of Arab states forged through the work of the Trump administration.

If President Biden manages to clinch a trilateral megadeal — which would probably include a Saudi-Israeli peace agreement, an Israeli commitment to a two-state solution, a U.S.-Saudi defense treaty and U.S.-Saudi understandings on a civilian nuclear program in Saudi Arabia — he will need support from two-thirds of senators to ratify the U.S.-Saudi treaty. Mr. Trump, as the presumptive Republican nominee in firm command of his party, could potentially either block any deal or greenlight it for congressional Republicans.

Mr. Trump has other reasons to maintain warm relations with Prince Mohammed. The former president and Jared Kushner, his son-in-law and former senior White House adviser, established close ties with the crown prince while in office and have capitalized on that good will in their private businesses since leaving government.

Saudi Arabia was the first stop on Mr. Trump’s first foreign trip as president — a sign of the value Mr. Trump placed on the relationship. Mr. Trump pursued major deals with the Saudis, including arms sales, and he defended Prince Mohammed at his moment of greatest international pressure, after the C.I.A. concluded that the crown prince had ordered the killing of the dissident journalist Jamal Khashoggi in 2018.

Nine months after the killing, Mr. Trump called Prince Mohammed “a friend of mine” and praised the “spectacular job” he had done in liberalizing Saudi Arabia’s laws, including allowing women to drive. While still in office, Mr. Trump told the journalist Bob Woodward that “I saved his ass” when Prince Mohammed was under intense criticism from officials in the U.S. Congress.

“I was able to get Congress to leave him alone. I was able to get them to stop,” Mr. Trump added.

For his part, Mr. Biden promised during his 2020 campaign to treat Prince Mohammed as a “pariah” because of the killing of Mr. Khashoggi. Once in office, however, he concluded that it was unsustainable to sideline the Saudi crown prince, and his team has sought to mend the fractured relationship.

Since leaving the presidency, Mr. Trump has made use of his Saudi connections. At the same time as he was preparing to announce his presidential campaign, in November 2022, the Trump Organization was putting the final touches on a deal with the Omani government and a Saudi firm for a multibillion-dollar Trump-branded real estate development in Oman. Mr. Trump has also worked with Saudi Arabia’s sovereign wealth fund to host the Saudi-backed LIV golf tour at some of his golf courses.

Mr. Kushner has benefited from Prince Mohammed’s support on an even larger scale. Only six months after leaving government, Mr. Kushner’s investment firm, Affinity Partners, secured $2 billion from Saudi Arabia’s Public Investment Fund, in what was described in internal documents as a “strategic relationship” with Mr. Kushner. A panel of advisers to the Saudi sovereign wealth fund had recommended against investing with Mr. Kushner, citing his lack of experience, but Prince Mohammed overruled them.

The Saudi crown prince is not the only foreign leader with whom Mr. Trump has engaged recently. Last month, he hosted Prime Minister Viktor Orban of Hungary at his Mar-a-Lago estate in Florida for a meeting, the second they have held in the last two years. A person close to Mr. Trump said it was Mr. Orban who sought the meeting.

At some of his rallies, Mr. Trump has lauded Mr. Orban — who has been criticized for eroding democratic institutions in Hungary — as an admirably strong leader.