When U.S. President Donald Trump visited Saudi Arabia last May, making it the first stop in his first foreign trip as president, he unleashed a wave of euphoria in the kingdom. The Saudis viewed Trump as a like-minded leader, whose ascent augured a future of closely coordinated foreign policy and firm advances for a U.S.-backed Saudi Arabian agenda in the Middle East. But five months later, in a twist few could have anticipated, Saudi King Salman landed in Moscow to meet with Russian President Vladimir Putin, signaling that Trump’s embrace of the kingdom has proved less fruitful than the Saudis had expected.

The arrival last week of Salman and a huge Saudi delegation—some 1,500 people—was a major event in Russia. Salman was the first reigning Saudi monarch to visit the Russian capital, and the streets were filled with posters promoting “Saudi Culture Week,” one of the many events held in conjunction with the Salman-Putin summit.

The visit was a recognition that Russia has become a major player in the Middle East. It was undoubtedly a feather in Putin’s cap, but its significance was far more than cosmetic.

While much of the Western media focused on the odd sight of the king’s golden escalator getting stuck as he descended from the royal aircraft, Russian and Arab outlets heralded the trip’s strategic significance.

Until now, Saudi Arabia has relied almost exclusively on its relationship with the United States to ensure its security. Since the iconic 1945 meeting between President Franklin D. Roosevelt and King Abdulaziz, the kingdom’s founder, the U.S. has protected Saudi Arabia in exchange for a steady supply of oil.

But the Saudis have grown wary of Washington. Concerns started when former President Barack Obama tried to repair relations with Iran, the Saudis’ archenemy. Trump was supposed to redirect U.S. policy in the Middle East, but so far he has failed to stop Iran’s growing strength in Iraq, Syria or Yemen, while his increasingly chaotic performance does not inspire confidence in Riyadh.

Against this backdrop, Salman’s Moscow trip must be seen as part of a push to widen Saudi Arabia’s foreign relations, and potentially reduce the kingdom’s reliance on Washington.

The top item on the agenda was oil, a topic on which Moscow’s and Riyadh’s interests coincide. The two countries’ economies have struggled as a result of the sharp drop in oil prices in recent years, and they are working together to limit oil supply in order to prop up prices. Saudi Arabia wants to make sure that Russia, a non-OPEC member, holds the line.

But the talks went far beyond oil—far enough that American strategists surely took notice.

Salman and Putin discussed the future of Syria and explored areas of economic and military cooperation, reaching agreements whose progress Washington and its allies will follow very closely.

Also watching with great interest, undoubtedly, was Syrian President Bashar al-Assad. The visit had to be cause for celebration at the presidential palace in Damascus. Throughout the almost six-year-old Syrian civil war, Riyadh has supported the rebels seeking to topple Assad. Now that Russian intervention has turned the tide of the war, Salman appears to be acquiescing to Assad’s survival.

That may or may not be good news for Iran, Assad’s top ally and benefactor. The Islamic Republic welcomes all signs that Assad will remain in place, securing its sway in Syria. But the rapprochement between Moscow and Riyadh surely creates some unease in Tehran, which worries about the Saudis interfering in its relationship with Russia.

Salman’s Moscow trip must be seen as part of a push to widen Saudi Arabia’s foreign relations, and potentially reduce the kingdom’s reliance on Washington.

In Moscow, Salman spoke out against Iran, telling Putin that Iran must stop meddling and “give up interference with the internal affairs of the region.”

If the Saudis can drive a wedge between Moscow and Tehran, Washington would be delighted. But for now, that seems unlikely, as Russia and Iran work together to secure a victory for Assad in Syria.

That didn’t stop Putin and Salman from signing a number of other agreements last week. Saudi Arabia agreed to make multibillion dollar investments in Russia, potentially punching a hole in Western sanctions by helping to fund technology, energy projects and new roads.

The two countries also signed a memorandum of understanding, reportedly committing Saudi Arabia to purchase the Russian S-400 missile defense system. The day after that announcement, the Pentagon said the U.S. had approved a $15 billion purchase by Saudi Arabia of the U.S.-built THAAD anti-missile defense system. Russian officials said the agreement on the Russian missile defense system was firm.

In addition to the S-400, the deal includes purchases of anti-tank Kornet rocket systems, automated grenade launchers, Kalashnikov rifles and other items.

The question for the U.S. is whether this array of agreements signifies the beginning of a major shift in Saudi Arabia’s allegiance.

The Russian media played up the strategic significance of Salman’s visit and the extent to which it confirmed Russia’s renewed standing as a major player in the Middle East.

Saudi diplomats in Moscow were waxing exuberantly about the bilateral prospects. Foreign Minister Adel al-Jubeir declared that “new horizons have opened up for the developments of our relations that we could not previously have imagined,” calling this a “historical moment.”

But al-Jubeir also took pains to reassure Washington. “We do not think that in developing relations with Russia, we damage [relations with the U.S.],” he said. “The more partners we have, the better for all.”

Unless the Saudis can convince Russia to move away from Iran, though, a closer relationship between Russia and Saudi Arabia is not better for the United States. Any influence Moscow gains in Riyadh potentially diminishes Washington’s.

It’s very possible that one of Saudi Arabia’s objectives with the trip was to send a message to Washington—which has wavered in supporting Riyadh in its dispute with Qatar—that the Saudis have choices.

If Putin was being used to send that message, he enjoyed it thoroughly. Asked about the close links between Riyadh and Washington, he replied with his own question. “Is there anything permanent in the world?” He answered that himself. “On the contrary, the world is changing all the time.”