WASHINGTON — On the afternoon of May 1, President Trump’s son-in-law, Jared Kushner, welcomed a high-level delegation of Saudis to a gilded reception room next door to the White House and delivered a brisk pep talk: “Let’s get this done today.”

Mr. Kushner was referring to a $100 billion-plus arms deal that the administration hoped to seal with Saudi Arabia in time to announce it during Mr. Trump’s visit to the kingdom this weekend. The two sides discussed a shopping list that included planes, ships and precision-guided bombs. Then an American official raised the idea of the Saudis’ buying a sophisticated radar system designed to shoot down ballistic missiles.

Sensing that the cost might be a problem, several administration officials said, Mr. Kushner picked up the phone and called Marillyn A. Hewson — the chief executive of Lockheed Martin, which makes the radar system — and asked her whether she could cut the price. As his guests watched slack-jawed, Ms. Hewson told him she would look into it, officials said.

Mr. Kushner’s personal intervention in the arms sale is further evidence of the Trump White House’s readiness to dispense with custom in favor of informal, hands-on deal making. It also offers a window into how the administration hopes to change America’s position in the Middle East, emphasizing hard power and haggling over traditional diplomacy.

“Both sides have an incentive to herald this as a new era in Gulf cooperation,” said Derek H. Chollet, who served as assistant secretary of defense for international security affairs under Mr. Obama. “I see this as largely continuity.”

What has changed, Mr. Chollet said, is that the House of Saud is now dealing directly with a member of the Trump family. “It’s quite normal for them to sit down with the son-in-law of a president and do a deal,” he said. “It’s more normal for them than any previous administration.”

The White House and Lockheed declined to comment on the call between Mr. Kushner and Ms. Hewson, or on the broader arms sale.

While Mr. Kushner’s middle-of-the-meeting call to a military contractor was unorthodox, current and former officials said, it did not appear to raise legal issues. Lockheed is the sole manufacturer of the antimissile system, known as Terminal High Altitude Area Defense, or Thaad. Instead, the episode was reminiscent of Lockheed’s decision in February to cut the price of F-35 fighter jets it was selling to the Pentagon after Mr. Trump complained to Ms. Hewson that the planes were too expensive.

Mr. Kushner, White House officials said, began building ties to members of the Saudi royal family during the transition. He was at the table when his father-in-law hosted the deputy crown prince, Mohammed bin Salman, at a lunch in the State Dining Room in March. And he offered a strategic overview of the Saudi-American relationship at the meeting this month, according to an agenda obtained by The New York Times.

But officials emphasized that Mr. Kushner’s work on the deal was part of a governmentwide effort that includes the State Department, the Defense Department and the National Security Council.

They also said the arms sale would be only one element of Mr. Trump’s busy two-day stop in Saudi Arabia, which will also include a meeting with King Salman at the royal court, a conference with Persian Gulf allies, a broader summit meeting with the leaders of Muslim countries, and a visit to a new center dedicated to combating terrorism and extremism.

The showcase event will be a speech in which the officials said Mr. Trump would seek to unify the Muslim world against the scourge of extremism. Stephen Miller, Mr. Trump’s senior policy adviser, is writing the speech, which officials said would serve as an answer to the landmark address to the Islamic world that Mr. Obama gave in Cairo in 2009.

White House officials have consulted Mr. Obama’s speech and predicted a starkly different tone from Mr. Trump. His goal, they said, will be to unify America’s allies around a common set of objectives, including a harder line against Iran and a pledge to share the security burden in the region. The speech will not include any apology for America’s role.

After a strained relationship with Mr. Obama, Saudi officials have expressed delight at Mr. Trump’s tough rhetoric on Iran. This White House is viewed as more sympathetic to the military campaign that Saudi Arabia and the United Arab Emirates are carrying out against the Houthis, Iranian-backed rebels who are waging an insurgency in neighboring Yemen.

The Obama administration put a hold on precision-guided munitions it had agreed to sell the Saudis out of fear that they would be used to bomb civilians in Yemen. The Trump administration has freed up those weapons, which are part of the $110 billion package.

The package also includes “maritime assets,” meaning ships, so the Saudis can assume more of the burden of policing the Persian Gulf and Red Sea against Iranian aggression. It does not include high-end items like the advanced F-35 fighter, whose sale to Saudi Arabia would alarm Israel.

Mr. Trump is not expected to raise human rights concerns with the Saudis, in keeping with his approach to strongmen in Turkey, Egypt, China and the Philippines. The president, his aides said, does not believe the United States gets results by lecturing other countries.

Given that, and the big-ticket arms sale, most analysts and former officials predicted that Mr. Trump’s visit to Saudi Arabia would be a success. It could end up being the highlight of his nine-day, four-country tour, particularly since he will be going later to a NATO summit meeting in Brussels, where the other attendees will watch for evidence that he still wants to mothball the alliance.

Even in Israel, where Mr. Trump is likely to be welcomed with open arms, tensions have surfaced over his sharing classified Israeli intelligence during a meeting with Russia’s foreign minister and ambassador to the United States, and a smaller flap over the political status of the Western Wall.

Still, the Saudi visit is not without risk. Mr. Obama made Riyadh, the Saudi capital, his first stop in the Middle East in June 2009, hoping to enlist the Saudis in a new Israeli-Palestinian peace effort. King Salman’s predecessor, King Abdullah, rebuffed the young president.

For now, the White House is not abandoning the Iran nuclear agreement, which is reviled in Saudi Arabia. Though experts say the Saudis understand the administration’s reluctance to act precipitously, some critics worry that it will make Mr. Trump more eager to accommodate the Saudis in other areas, like their campaign in Yemen.

“We’d been saying for two years that this is not a conflict you’re going to win militarily,” said Jeffrey Prescott, a senior director for Iran, Iraq, Syria and Gulf nations on Mr. Obama’s National Security Council. “We had been trying to use the leverage we had to get the Saudis and Emiratis to the table to negotiate.”

“One of the things to look at,” Mr. Prescott added, “is whether we’re getting into someone else’s conflict.”