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That Donald Trump has been reluctant to pressure Saudi Arabia should be clear by now. Yeah, Trump warned about "severe punishment" if it turned out the Saudi government was responsible for Washington Post contributor Jamal Khashoggi's death, but his heart wasn't in it. Despite massive corporate cancellations to Saudi Arabia's "Davos in the Desert" conference, Treasury Secretary Steven Mnuchin still planned to attend as of Tuesday. When asked over the past week about the question of pressuring Saudi Arabia over Khashoggi's disappearance, Trump has given one of two kinds of responses. The first is to stress Saudi Arabia's denial:

"Just spoke to the King of Saudi Arabia who denies any knowledge of whatever may have happened 'to our Saudi Arabian citizen.' He said that they are working closely with Turkey to find answer. I am immediately sending our Secretary of State to meet with King!" Trump tweeted Oct. 15.

As Post writer Aaron Blake observes, Saudi Arabia now joins the coveted club of inner-circle Trump cronies who, by denying things, get off the hook: Crown Prince Mohammed bin Salman, Rob Porter, Kim Jong Un, Roy Moore, Vladimir Putin and Brett Kavanaugh, among others.

The second kind of Trump response is to suggest that the United States lacks leverage because any pressure would jeopardize massive arms sales to Riyadh. There are several dubious dimensions to this. Post Fact Checker Glenn Kessler found the claim of $110 billion in arms sales to Saudi Arabia seriously wanting:

"Most of the publicly announced items had been previously announced by the Obama administration and there appeared to be few, if any, signed contracts. Rather, many of the announcements were MOIs - memorandums of intent. There were six specific items, adding up to $28 billion, but all had been previously notified to Congress by the Obama administration. . . .

"A review of the announcements on the Defense Security Cooperation Agency website since Trump's 2017 trip reveals that, besides 1/8the Terminal High Altitude Area Defense system3/8, there have been six State Department announcements of approval of Saudi sales, totaling just $4 billion.

"According to the confidential 2017 document of all of the military-sales agreements reviewed by The Fact Checker, most of the items did not have delivery dates or were scheduled for 2022 or beyond."

Meanwhile, Naval War College professor and arms sales expert Jonathan Caverley wrote in the New York Times that in the U.S.-Saudi relationship, the United States had significantly more leverage:

"Saudi Arabia is in the middle of a major war, and more than 60 percent of its arms deliveries over the past five years came from the United States. The Saudi military relies not just on American tanks, planes and missiles but for a daily supply of maintenance, training and support, such as intelligence and refueling. In the longer term, almost all of Saudi Arabia's remaining exports come from Europe. To truly squeeze Saudi Arabia, a coordinated embargo - much like the one now in place against Russia - would be necessary but relatively easy. European governments already feel strong domestic political pressure not to export to regimes like Saudi Arabia.

"Transforming the Saudi military to employ Russian, much less Chinese, weapons would cost a fortune even by Gulf standards, would require years of retraining and would greatly reduce its military power for a generation. Russia cannot produce next-generation fighter aircraft, tanks and infantry fighting vehicles for its own armed forces, much less for the export market. China has not produced, never mind exported, the sophisticated aircraft and missile defense systems Saudi Arabia wants."

As for the oil weapon, any oil embargo would devastate Saudi interests far more than American interests.

Let's pause to contrast Trump's manifest reluctance to pressure Saudi Arabia with his visible glee at coercing literally every other U.S. major treaty ally outside the Middle East. The administration's steel and aluminum tariffs managed to encompass Japan, South Korea, Canada, Mexico and our European NATO allies. Trump's withdrawal from the Iran deal is designed to pressure Iran - by actually pressuring European firms. This administration has adopted the most hostile policy toward the European Union in the history of European integration. Trump told "60 Minutes" that "the E.U. was formed to take advantage of the U.S."

Despite the deep web of economic interdependence between the United States and these treaty allies, this administration has been prepared to sanction them across a wide array of issues. The results have mostly been token concessions and a collapse of American soft power, but the sanctions have been fast and furious nonetheless.

What explains Trump's reluctance to apply economic pressure on Saudi Arabia? In "The Sanctions Paradox," I argued that sanctioning states would be deeply reluctant to coerce close allies even if there was asymmetrical dependence. The gap in costs would have to be so massive that the sanctioner thought it was worth it to extract tangible concessions.

When it comes to sanctioning Canada, Japan, Mexico, South Korea and the European Union, Trump sees adversaries and believes it is worth risking deadlock to gain a slightly more favorable balance of trade. Trump treats Saudi Arabia as a true ally, however. He is reluctant to sanction it for any reason. Furthermore, Trump cares so little about human rights that any concessions in this arena are worse than useless in his mind.

Realists and liberals disagree a lot on many aspects of U.S. foreign policy. One area of consensus, however, is that Saudi Arabia is not a more important ally than, say, the United Kingdom or Japan. Nonetheless, Trump's behavior since Khashoggi's disappearance shows that this is exactly how he prioritizes U.S. allies. Which says a lot about how Trump sees the world, and none of it is good.

Drezner is a professor of international politics at the Fletcher School of Law and Diplomacy at Tufts University.