Russian President Vladimir Putin (third from left), Iranian President Hassan Rouhani (fourth from left) and Turkish President Recep Tayyip Erdogan (second from left) leaving a joint statement about their meetings Sochi, Russia to discuss Syria on Nov. 22. (Michael Klimentyev/Sputnik/Kremlin pool/EPA-EFE/REX/Shutterstock)

Frida Ghitis is a columnist for World Politics Review and a regular CNN.com opinion contributor.

It is a partnership that would have been inconceivable just a few years ago, and one that should come as a warning to Washington. Today, Russian President Vladimir Putin hosted a trilateral summit with the presidents of Iran and Turkey in Russia’s Black Sea resort city, Sochi. Putin, who gave a warm welcome to Syrian President Bashar al-Assad yesterday, declared that the three countries deserve credit for helping to maintain “stability” in Syria.

The meetings are centered on the future of Syria now that the so-called Islamic State has been pushed back and the future of the country — and the region — is in play. The fact that the future of Syria is being largely determined without significant input from Washington, the world’s single superpower, shows how fast American muscle is weakening.

President Trump has all but declared war on diplomacy, steadily grinding down the State Department to a shell of its former self. He has downplayed relations with some of America’s friends while lavishing effusive praise on some its greatest foes. Now, other countries are stepping into the breach.

As Trump’s State Department under Secretary of State Rex Tillerson moves forward with a campaign apparently aimed at contracting American diplomacy, slashing the budget and shedding large numbers of experienced diplomats, everywhere large and medium powers are eagerly moving into the space vacated by the United States.

The U.S. still has the world’s largest military, by an enormous margin, but when it comes to power, military might alone is not enough. As recent developments in Syria show, the United States’s rivals and adversaries are working just as hard at forging new alliances as the Trump administration is at dismantling American diplomacy. As a result, Washington is not only less involved, but also less influential, less able to shape events and outcomes and potentially less secure. In short, the United States is less powerful.

Today’s trilateral summit is even more remarkable because it brings together countries that are not natural allies and have a history of occasionally intense acrimony. But at this very pivotal moment in Mideast history, they are jumping at the chance to sideline the United States in pursuit of their own interests. Those interests, for the most part, do not align with America’s.

To be sure, former president Barack Obama’s Syria policy was deeply flawed. But Trump’s Syria policy is largely unknown, beyond Trump’s interest in continuing the obliteration of ISIS positions.

Russia moved in early to fill the vacuum left by the Obama administration, becoming once again a key player in the Middle East. Regional leaders come courting.

Just a few years ago, Russia and Turkey appeared to be on the verge of war after Turkey shot down a Russian fighter jet. But all that is now in the past. Putin and Turkish President Recep Tayyip Erdogan have become close. The meeting this week will be their sixth this year. Just last week, Erdogan traveled to Russia and met with Putin for four hours.

Turkey, remember, is a NATO member, a U.S. ally. But even though Erdogan wanted to see Syria’s Assad regime deposed, which Russian intervention in Syria’s war averted, Erdogan and Putin are now working together.

Turkey also has a history of acrimonious relations with Iran, one of America’s top foes. But Turkey and Iran have come together. They are on the same side of the dispute between Saudi Arabia and Qatar, and they jointly oppose Kurdish separatism. Erdogan, meanwhile, continuously attacks the United States, even claiming that Washington deliberately created ISIS and Al Qaeda.

Aside from their shared interest in Syria, this emerging tripartite alliance seems to share something else: opposition to American goals.

While the Trump administration has been trying to push back against Iran’s regional power, Russia is moving in the opposite direction. Russian Foreign Minister Sergei Lavrov recently declared that “the presence of Iranian forces in Syria is legitimate,” all but greenlighting a continuing presence by the Islamic Republic there, much to Israel’s alarm. Erdogan and Putin have also confirmed that Turkey plans to buy a Russian-made missile system, sparking stern warnings from NATO.

Syria is not the only place where the U.S. is losing ground. America’s influence is visibly waning in Asia, where Trump seems to have opened a wide berth for China to flex its muscles.

In Latin America, Russia is making strides, even as Trump manages to simultaneously anger and neglect the region. Trump’s campaign rhetoric against Mexicans was heard loudly in the hemisphere. And when he threatened military action against Venezuela, Latin America cringed, even if most there would like to see the end of the disastrous Maduro regime.

Despite Trump’s crackling rhetoric, Iran is steadily gaining influence and power. Allowing Iran a permanent military presence in Syria, linking Tehran to Syria and Lebanon, and at Israel’s doorstep, would mark a failure to meet Trump’s own stated goals.

Trump has talked a tough game. But so far under his watch, the United States has been losing ground to rival powers. If his objective is to make the United States a country with less global influence, he is achieving his goals. Otherwise, it’s time to try a different approach. In the meantime, keep an eye on that budding friendship between Iran, Russia and Turkey.