Smiles and handshakes punctuated Secretary of State Mike Pompeo's visit to Saudi Arabia this week as America’s top diplomat said he was trying to get to the bottom of the disappearance of the Saudi journalist Jamal Khashoggi.

Pompeo got a warm welcome from both King Salman and Crown Prince Mohammed bin Salman, the kingdom’s putative leader. Yet the U.S. response to the disappearance and feared murder of Khashoggi, a columnist for The Washington Post, allegedly at the hands of Saudi officials, is complicated by a relationship that stretches back more than seven decades.

Saudi Arabia and the United States are “strong and old allies so we face our challenges together," the crown prince said upon greeting Pompeo in Riyadh on Tuesday.

"Absolutely," Pompeo responded.

President Franklin D. Roosevelt and King Abdul Aziz discuss Saudi-U.S. relations aboard the USS Quincy north of Suez, Egypt, on Feb. 14, 1945. AP file

This is not a match built on shared democratic values. Saudi Arabia is an absolute monarchy and religiously conservative. But even if it and the U.S. are far apart culturally, the countries' interests are intertwined when it comes to trade and oil, and the fight against an expanding Iran.

Regarding the disappearance of Khashoggi, a longtime regime insider who left Saudi Arabia last year amid the crown prince's crackdown on dissent, the two countries may be trying to reach common ground in order to not disrupt relations, analysts say.

"I can see a lot of people shifting around and trying to get through this without a major breach," said David Butter, an associate fellow at the London-based think tank Chatham House. "It's not clear how that will be achieved unless things are allowed to slide and it's accepted that there will be some fall guys that the Saudis will blame."

In 2017, U.S. and Saudi Arabia's trade in goods and services was worth over $45 billion, with top exports from the U.S. including aircraft and weapons. The kingdom is also the 10th-largest holder of U.S. Treasury bills and notes, currently worth around $166 billion, according to the Treasury Department.

Trump underlined the economic relationship when he said on Saturday that if the Saudis "don’t buy it from us, they’re going to buy it from Russia or they’re going to buy it from China," referring to an arms deal he helped broker. "Think of that, $110 billion. All they’re going to do is give it to other countries, and I think that would be very foolish.”

Oil has also linked the two countries since before World War II, when America oil companies helped the kingdom develop the sector. The relationship between the United States and Saudi Arabia has always been likened to a marriage of convenience: the United States provides security in return for Saudi Arabia, the world's largest oil exporter, ensuring affordable oil supplies for the global economy.

With U.S. sanctions on Iran, a fellow oil exporter and fierce Saudi regional rival, set to deepen in November, the Trump administration was planning to rely on Riyadh to make up for the shortfall.

When Trump came to power he focused on Saudi Arabia and made the kingdom his first visit overseas as president. At the time, White House officials told reporters that Saudi leaders would help drive a Palestinian-Israeli peace deal, as well as develop a long-term plan to cut Islamic State funding and get those in the region to contribute more to the fight.

In spite of the ties, U.S. lawmakers have taken a tougher stance than the president in the wake of Khashoggi's disappearance.

Sen. Lindsey Graham, R-S.C., normally a Trump ally, said on Tuesday said that he believes that the crown prince had Khashoogi "murdered" in the Saudi consulate in Istanbul and that he has "tainted" his country as a result. Graham added that the crown prince "has got to go" and that he now plans to "sanction the hell out of Saudi Arabia."

The Senate’s foreign policy lawmakers have signaled bipartisan support for punishing the Saudis with sanctions. Last week, more than 20 senators triggered the Global Magnitsky Human Rights Accountability Act, which prohibits extrajudicial killings, torture and other egregious rights violations. Under the law, Trump must report within 120 days as to whether gross rights violations have occurred, and if so, who in Saudi Arabia should be held responsible and targeted with sanctions.

Even before Khashoggi’s case, lawmakers expressed increasing frustration with Saudi Arabia, condemning Riyadh over its military campaign in Yemen that has claimed thousands of civilian lives and helped cause a humanitarian catastrophe. Congress has only narrowly approved recent arms sales to Saudi Arabia and has demanded the Trump administration certify whether the Saudi-led coalition is abiding by the laws of war in Yemen.

For all the hostility directed at the Saudis, however, lawmakers are reluctant to back drastic steps that could jettison the longstanding partnership with the kingdom, according two Senate staffers, one Republican and one Democratic, who asked not to be identified because they were not authorized to speak on the record. Instead, Congress wants to see punishment meted out while preserving the strategic alliance, and the Trump administration appears to be pushing in that direction, the staffers said.

Asked about the possibility of sanctions on specific sectors of the Saudi economy, or those that target major Saudi state companies, the Democratic staffer told NBC News: “It’s too early for that.”

The two economies have an array of connections and “we have to make sure we don’t shoot ourselves in the foot.”

There is also talk of potentially rejecting future arms sales — the country is the largest recipient of U.S. arms — although there is still a reluctance to take more drastic measures that could upend the U.S.-Saudi relationship.

The Khashoggi case is not the first time the U.S.-Saudi relationship has come under pressure. Tension increased during the presidencies of both George W. Bush and Barack Obama. In the Sept. 11, 2001, terror attacks, 15 of the 19 attackers hailed from Saudi Arabia. Still, Bush ended up overseeing a huge increase in the number of Saudi students in the U.S., in an effort aimed at increasing cultural understanding.

In the final months of his presidency, Obama vetoed a bill supported by members of his own party that would have allowed the families of 9/11 victims to sue Saudi Arabia — a sign of how seriously the administration took the relationship.

Officials in Saudi Arabia, deeply embarrassed by its association with the attacks and ashamed that Osama bin Laden, the Qaeda leader who plotted the attacks, was himself from a prominent Saudi family, have more recently passed laws aimed at limiting support of violent extremism.

Adam Coogle, a Middle East researcher with Human Rights Watch, said the long-standing economic and security ties with Saudi Arabia have forced the U.S. to tolerate a lot of questionable Saudi behavior.

"When the U.S. fails to prioritize human rights concerns, it gives the Saudis a green light to keep doing what they are doing," he said.

Coogle said he hoped the Khashoggi disappearance and the negative attention it has heaped on Saudi Arabia will finally galvanize the U.S. to be critical of the kingdom and do more than express a message of concern.

"We have seen a few blow-ups over the years, but nothing that’s had the momentum of this," he said.

"Part of it has to do with the fact that everybody knew Jamal," Coogle said. "Everybody who has worked on Saudi in journalism or foreign policy had met him because he was one of the guys you’d talk to. It's the absolute gruesomeness of the crime, if it's true, and the total disregard for any international norms that makes it stand out."

But the close ties between the U.S. and Saudi Arabia — and this White House and this crown prince — will probably slow any efforts to distance Washington from Riyadh.

On Tuesday, Trump warned against rushing to judgment on the Khashoggi case.

"Here we go again with, you know, you're guilty until proven innocent,” he said, before comparing the situation to allegations of sexual assault against Supreme Court Justice Brett Kavanaugh during his confirmation hearing.

Reuters contributed to this article.