International concern over Saudi Arabia’s suspected role in the disappearance of a prominent Saudi journalist has threatened to disrupt one of the United States’ most important security partnerships.

Reports that Jamal Khashoggi, a Washington Post columnist and critic of Saudi Crown Prince Mohammed bin Salman, was killed in the Saudi Consulate in Istanbul this month have sparked a wave of criticism of the kingdom and questions about whether President Trump and his top aides have emboldened the young royal.

While the Trump administration has reacted cautiously to reports that Saudi Arabia is responsible for Khashoggi’s disappearance, lawmakers have demanded a strong U.S. response, potentially including steps to curtail arms sales or affect other aspects of U.S. defense ties with the kingdom.

On Friday, Sen. Dianne Feinstein (D-Calif.) called for a broad halt to military cooperation if ­Saudi responsibility is established, adding her voice to a growing roster of lawmakers linking security ties to Khashoggi’s fate.

“Saudi Arabia was once one of our closest allies in the Middle East,” Feinstein said in a statement. “I think now is the time to reevaluate that relationship.”

Some lawmakers have called for sanctions or suspension of military aid to the kingdom’s war in neighboring Yemen. Others have said there may be “hell to pay,” as Sen. Lindsey O. Graham (R-S.C.) put it this week, if the kingdom is found responsible.

But Trump, who has made the Saudi monarchy his premier Arab ally, waved off those demands, telling reporters that cutting off sales to the world’s largest buyer of U.S. weaponry “would not be acceptable to me.”

“If we don’t sell it to them, they’ll say, ‘Well, thank you very much. We’ll buy it from Russia.’ Or ‘Thank you very much. We’ll buy it from China,’ ” Trump said. “That doesn’t help us — not when it comes to jobs and not when it comes to our companies losing out on that work.”

The president’s comments may say as much about his transactional view of foreign relationships, elevating economic concerns over human rights, as they do about the centrality of arms sales to the two countries’ defense relationship.

For decades Saudi Arabia has been an important American military partner in the Arab world, where its status as the home to Islam’s holiest sites boosts its leadership credentials. Since the Sept. 11, 2001, terrorist attacks in the United States, the kingdom has played a critical role in U.S. counterterrorism efforts, supplying the government with valuable intelligence about extremist threats.

Most significantly, Saudi Arabia has used petrodollars to build up the Arab world’s most sophisticated military arsenal. With one of the world’s largest military budgets, the kingdom boasts a large fleet of F-15 and Tornado fighter jets, Apache helicopters and other advanced aircraft.

About $14.5 billion in major sales have been concluded with Saudi Arabia since Trump became president, but much or all of that was initiated before he took office.

The potential for a shut-off to the lucrative arms pipeline has alarmed the defense industry.

The sales are even more significant for the administration because, unlike Israel and Egypt, Saudi Arabia uses its own money rather than U.S. aid to finance arms purchases.

Although Congress has the power to broadly halt arms sales or suspend military aid, lawmakers have so far declined to do so. The Obama administration, frustrated by Saudi attacks on civilian sites in Yemen, temporarily halted sales of precision munitions in 2016, but Trump reversed that move after taking office.

For Saudi Arabia, the race to arm itself has been aimed not just at boosting its fighting power but also deepening political ties with producer nations like the United States. The favor those sales have curried was starkly visible in Trump’s Oval Office comments this week.

But analysts and former officials said the cultivation of Saudi Arabia as the top U.S. arms customer had not yet turned the kingdom into Washington’s essential military partner in the Arab world.

“In terms of the military or security benefit we get, there’s no automatic translation from those weapons into an operational capacity unfortunately,” said Andrew Miller, deputy director for policy at the Project on Middle East Democracy. “There would need to be more of an emphasis on training and less of an emphasis on the systems themselves.”

Saudi Arabia’s military performance has been hobbled by a number of issues, analysts said, including shortcomings in logistics and maintenance, a weak noncommissioned officer corps and a system for military appointments based on connections rather than merit.

Saudi Arabia has requested less hands-on training from the U.S. military than some other Arab nations. It also relies on outside help to maintain much of its high-tech weaponry.

“The bang they get for that large buck is extremely low,” said Thomas Juneau, an assistant professor at the University of Ottawa and a former analyst at Canada’s Department of National Defense. “It’s especially shocking given how much money they spend and the fact they have some of the most advanced systems in the world.”

American military officials continue to see elite forces from the United Arab Emirates, Jordan and Iraq as their preferred tactical ground partners among Arab nations.

The war in Yemen, where Riyadh is leading a coalition of nations battling Houthi militants linked to Iran, has laid bare those challenges as Saudi Arabia remains mired in an expensive war it started over U.S. objections more than three years ago.

The kingdom maintains a small force on the ground, relying on local and third-country forces to battle the Houthi troops. Saudi planes have repeatedly struck civilian sites, raising questions about their targeting practices and, for the first time, stirring a growing tide of opposition in Congress. Lawmakers have delayed one major sale because of concerns about civilian harm and have advanced proposals that could block U.S. military aid to the Yemen operation, which includes aerial refueling and intelligence sharing.

The war in Yemen also has diminished Saudi ability to contribute to the campaign against the Islamic State, the chief U.S. counterterrorism mission of recent years. Saudi Arabia participated in the opening days of the U.S.-led coalition’s air war in Syria but, like other Middle Eastern countries, has distanced itself from that fight since then.

More recently, Trump suggested the kingdom might send troops to pacify Syria, but that has not occurred. Greater military cooperation among Gulf nations also has failed to materialize along the line of a U.S. proposal, in which officials hoped Riyadh would play a leading role, to create a regional alliance dubbed “the Arab NATO.” The initiative has become bogged down by conflicting visions for the alliance and a bitter feud with fellow Gulf nation Qatar.

Bruce Riedel, a former CIA and White House official, said U.S. and Saudi intelligence cooperation had long been more reliably beneficial for the United States than the two country’s military alliance. For years, Saudi officials have fed their American counterparts information about Islamist groups or plots against the United States. But Riedel said the quality of that intelligence has deteriorated since Mohammed took over as the country’s de facto ruler and pushed out the former intelligence chief.

Brian Katulis, a senior fellow at the Center for American Progress think tank, said recent events in Istanbul brought to a head questions about the Trump administration’s decision to designate the kingdom as its primary partner in the Arab world.

“If your whole Middle East strategy is premised on the idea that we’ve got to work directly through Riyadh, but Riyadh has shown itself to be such a flawed partner, it raises questions about what we’re doing,” he said.

Greg Jaffe and Karen DeYoung contributed to this report.