America’s most important partner in the Middle East is flirting with China. The dreaded “D” word — divorce — has been metaphorically uttered, Mohammed Alyahya, the Saudi formerly at the helm of Al Arabiya English tells me over lunch. Our strategic partnership with Saudi Arabia is fraying, and pro-American Saudis like Alyahya are concerned. 

The cause? President Biden’s criticism of the Saudi crown prince, Mohammed bin Salman, over his alleged involvement with the killing of journalist Jamal Khosoggi, the war in Yemen, and other human rights abuses.

On the campaign trail, Mr. Biden promised to “make them” — meaning the Saudis — “the pariah they are,” and not “sell any more weapons to them.” He declared, “There is very little socially redeeming value in the present government in Saudi Arabia.”

To some extent, the Saudis are accustomed to American politicians criticizing them over domestic affairs. Mr. Biden doubled down once elected, though, with the administration reiterating that “we’ve made clear from the beginning that we are going to recalibrate our relationship with Saudi Arabia.”

At that point, the Saudis began to wonder if they should take the Americans’ word for it, and devise a backup plan. I’ve heard that from a number of Saudis. The Chinese, they note, have been insistently knocking at the door. 

Maybe, their thinking goes, we should give the Chinese a serious look. Especially, they argue, when the United States is moving against the Saudis’ core national interests. Mr. Biden is poised to sign a new agreement with the Iranians that paves the way for them to get a nuclear weapon, and fills their coffers with tens, if not hundreds, of billions of dollars.

From the Saudi perspective, this is a nightmare. Nor are their fears unfounded. In February, the administration told Congress the Iranians were “weeks” away from a nuclear breakout point. Reports have it that the new Iran deal would sunset in nine years, leaving the Iranians free to move toward a bomb unencumbered.

In 2015, the last time a deal was struck, the Iranians used the cash and went on a deadly spree, funding fighters in Syria, Iraq, Lebanon, and, most dangerously for the Saudis, Yemen. The Iranian-backed Houthis attacked Saudi soil repeatedly, with missiles reaching Riyadh. The Iranians attacked, shutting down the Saudis most important oil processing facility. 

So, they ask themselves, is the United States still our partner? Are our interests still aligned? And it’s starting to look like the answer might be no. The Saudis are not all that sure we have their backs. So they are devising a back plan with the rising power courting them from the East, a nation attempting to pull our key ally to their side. 

What do the Chinese want from the Saudis? Exactly what we have wanted all these years. A strategic partnership with the one country able to increase or decrease oil production by 2 million barrels virtually overnight. This only the Saudis can give — and it certainly comes in handy. 

President Trump understood this. His first overseas trip as president was to the Saudi Kingdom. He used the Saudi ability to maneuver on oil in the early days of the pandemic, and when demand collapsed Mr. Trump leveraged the America-Saudi relationship to cut production and stabilize prices. The Saudis obliged, and crisis was averted.

President Biden sought to pull this very same handle last week, to mitigate already sky-high oil prices rising still further following President Putin’s invasion of Ukraine. This time, the Saudis did not oblige. The crown prince declined to take Mr. Biden’s call.

Suit was followed by the United Arab Emirates, whose own crown prince, Mohammed bin Zayed, MbZ, is close to MbS. It’s unfortunate that it took a war between Russia and Ukraine for the Biden administration to remember the central importance of an imperfect ally.

What do the Saudis want from China? Just what they want from us — a partner that can maintain stability in their neighborhood, keep the strait of Hormuz open for oil exports, and, critically, keep the Iranians in line. If the United States refuses to provide that, they say, they’ll have to go elsewhere. 

Some Saudis will go so far as to argue that the Chinese, as Iran’s main customer, may be more effective at keeping Iran in its box.  Plus, they say, Chinese weapons are much improved. Whether those weapons are counterfeit versions of American weapons is irrelevant. 

The Chinese, the Saudis will explain, are already the Saudis’ biggest trading partner, buying a quarter of Saudi oil exports. They have an enormous stake in Saudi Arabia’s stability given their dependence on its oil, and its free flow. They are willing to sell us equipment America won’t. And the cherry on top? They don’t bother us about human rights. 

No wonder the Saudis have become more open to Chinese overtures, and have moved the relationship from management to investment mode.  President Xi has accepted an  invitation from the Saudis and will soon make Riyadh his first foreign trip since the pandemic began. This important visit comes on top of a flurry of bilateral activity. 

Saudi Arabia and Communist China have signed dozens of economic cooperation agreements worth billions of dollars. Chinese will increasingly be added to the curriculum in Saudi schools and universities. A free-trade agreement between China and the Gulf Cooperation Council is being negotiated. The Saudis are even thinking about selling the Chinese 5 percent of ARAMCO in a private placement. 

The military relationship, too, is developing rapidly. For years, the Chinese have sold to the Saudis drones that America won’t. The People’s Liberation Army is helping the Saudis build their own ballistic missiles, something America has also long refused to do. The two militaries have begun to train together. 

The Chinese have also helped the Saudis build a uranium plant for their civil nuclear program, perhaps creating an insurance policy should Iran acquire a nuclear weapon and Saudi Arabia feel the need to do the same.

Most recently, the two countries have accelerated negotiations to price some oil sales in yuan, a move that would undercut the dollar’s dominance and boost the yuan’s at a time when the United States is depending on the dollar’s centrality to impose sanctions on Vladimir Putin.

The United States should be watching with horror, and acting to save its relationship with Saudi Arabia before it’s too late. We may not always see eye to eye, but the relationship has been fruitful.  And the Middle East writ large will remain strategic for decades to come. 

This is a time to bring our allies closer, and build new alliances, not lose our most important friends. The Saudi and the U.S. value systems have always been very different. That was true in the 1970s, it was true in the ’80s when we collaborated on the defeat of the Soviet Union in Afghanistan, and it remains true. If anything, our two societies are closer together today than ever before. The key thing that appears to have changed is America’s tolerance for working with people with whom we sometimes disagree.

The reality is, we need each and every ally and partner we can get, especially as we seek to build a coalition capable of withstanding Chinese aggression and expansion. Who else is capable of acting with us in the region? Iran, which shouts, “Death to America”? Iraq, which is riven with conflict? Syria? Lebanon, a state hijacked by Hezbollah? War-torn Yemen? Neutral Oman? 

Putting Israel aside, that leaves Egypt, Jordan, the United Arab Emirates, Kuwait, Bahrain, and Saudi Arabia, the undisputed leader among them. We should be capitalizing on the cohesion enabled by the Abraham Accords, not handing Saudi Arabia, and the Gulf states that will inevitably follow, to the Chinese.

A Middle East, and an oil supply, controlled by the Chinese would give China unacceptable leverage over the United States, and the world — and it would surely not improve the region’s human rights record, nor our climate goal. Thankfully, our history runs deep; because this is a future we must avoid at all costs.

Ms. Vik previously served as the Saudi Country Director at the Department of Defense. 

This version has been updated.