President Trump shakes hands with Saudi Defense Minister and Deputy Crown Prince Mohammed bin Salman on March 14. (Evan Vucci/Associated Press)

Philip Gordon is a senior fellow at the Council on Foreign Relations. He is a former assistant secretary of state and was White House coordinator for the Middle East from 2013 to 2015.

When President Trump touches down this weekend in Saudi Arabia for his first foreign visit, he can be sure of getting a warm reception. The Saudis have made no secret of the fact that they had real differences with the Obama administration — which they believed did not back them as vigorously as necessary in their regional competition with Iran — and they have good reason to think Trump may be different. When Saudi Deputy Crown Prince Mohammed bin Salman visited the White House in March, he described Trump’s election as “a historic turning point in bilateral relations of the two countries” and heaped praise on the new president’s understanding of the challenges facing the Middle East. It is not surprising that, according to leaked documents, the Saudis plan to spend some $68 million to give Trump the extravagant reception he adores.

It is easy to see why the Saudis are so hopeful about Trump. He says he’s going to take a much tougher stance against Iran and the Islamic State, two of Riyadh’s biggest enemies. He has heaped praise on Egypt’s president, Abdel Fatah al-Sissi, whom the Saudis see as a key ally in the region and bulwark against Islamist extremism. He will end the traditional U.S. practice of pressing regional leaders on democracy and human rights, a long-standing irritant in U.S.-Gulf relations. And Trump has expressed unambiguous support for Riyadh’s military campaign in Yemen, seen by the Saudi leadership as a vital national interest.

But the Saudis and others in the region should be careful about hitching their stars too closely to the Trump wagon. In the short run, Trump may say what they want to hear and offer some marginal additional support on policy issues. In the longer run, he is likely to prove an unreliable partner whose incompetence, disloyalty and unpopularity could prove costly to all concerned.

First, for all the differences in tone, it is far from clear that Trump’s approach to the Middle East will prove that different — or more successful — than his predecessor’s, even from a Saudi perspective. Trump talks tough on Iran, yet seems determined to preserve the allegedly “disastrous” nuclear deal. So far on Iran, there has been little to the “new” policy beyond a few additional sanctions and the announcement of a policy review. On Syria, far from expanding Barack Obama’s limited efforts to oust the Iran-backed Assad regime, Trump is abandoning them. His strategy to combat the Islamic State is turning out to be essentially the same as Obama’s, and on Egypt, Sissi may have gotten an Oval Office visit but seems unlikely to get much more than that, certainly not when it comes to the cash Cairo so badly needs and which the Saudis are tiring of paying. On Yemen, Trump has sent more Special Operations forces and advanced munitions to support the Saudi military operation, but it remains to be seen how long that support will be sustained if, as is likely, that war drags on and becomes increasingly unpopular in the United States.

Second, the Saudis should keep in mind that Trump is exceedingly transactional and focused only on his own — often personal — interests. In exchange for all he is doing for them, it will not be long before he starts to expect favors (beyond mere praise and a royal welcome) in return. It could start with additional investments in the United States and expand to preferential treatment of U.S. airlines, Arab steps to normalize relations with Israel, Gulf payments for “safe zones” in Syria, public defenses of Trump’s immigration policies, and of course business deals to the benefit of Trump businesses. The price for U.S. support could rise over time, while a failure to pay up could cause resentment and vindictiveness. This would not be the first business relationship with Donald Trump to turn sour, and if the Saudis think friendship or loyalty will provide them cover, they are not familiar with his track record.

Third and most important, Trump will not be around forever. He is already the most unpopular president at this point in a new administration, and all signs are that his standing will plummet further as failures and scandals accumulate. The Saudis and others should ask themselves whether they really want to be so closely tied to a president whose domestic agenda is frozen in Congress and the courts, whose presidential campaign is under FBI investigation, who is being credibly accused of obstruction of justice and who, days before his trip, allegedly imperiled the life of a secret agent through an extraordinary lack of self-discipline and judgment.

Mohammed, the deputy crown prince, likely one day to be the Saudi king who will rule for decades to come, should recall the experience of another young leader who sought to cozy up to a failing U.S. president for the sake of short-term bilateral relations. That was British Prime Minister Tony Blair, who 15 years later is still paying the price for his embrace of George W. Bush, who left office after the Iraq War and Hurricane Katrina with a 22 percent domestic approval rating. And there is a good chance that Trump ends up making Bush look wildly popular by comparison.

So if I can permit myself some advice to my Saudi friends, by all means give Trump the royal treatment and look for ways we can work together. But for the sake of our relationship, don’t put all your eggs in that basket, and keep the longer term in mind.