Russian President Vladimir Putin welcomes Syrian President Bashar al-Assad. (Sputnik/Reuters)

WITH THE near elimination of the Islamic State in Syria, there has been a fresh burst of diplomatic activity aimed at ending the country's civil war. A new session is scheduled Tuesday of U.N.-sponsored talks in Geneva following conferences last week hosted by Russia and Saudi Arabia and an hour-long phone call between President Trump and Vladi­mir Putin. The public statements and background briefings about the latest process have been contradictory and confusing. But a single photograph offers a simple and eloquent summation: that of the bearhug delivered by Mr. Putin to blood-drenched Syrian dictator Bashar al-Assad when they met in Sochi, Russia, last week.

The embrace was Mr. Putin's way of celebrating his success in rescuing the Assad regime from military defeat and propelling it to a string of victories over the Western-backed opposition in the past two years. It also eloquently communicated Mr. Putin's objectives in the coming diplomacy: sustaining the regime in power indefinitely, providing a new platform for Russia in the Middle East and marginalizing the United States.

Unfortunately, Mr. Trump appears more than happy to abet that project, which would also consolidate Iran's entrenchment in Syria. Following his phone call with Mr. Putin, he enthusiastically endorsed Mr. Putin's plans, which nominally entail new negotiations between the Assad regime and opposition groups over a new constitution. Turkey and Iran are lined up behind the Russian leader, who hosted their presidents in Sochi immediately after hosting Mr. Assad. Saudi Arabia, too, is playing along: Last week it convened a meeting of opposition groups to form a joint negotiating team — after purging nearly a dozen longtime rebel leaders who refused to accept Mr. Assad's continuance in power.

Trump administration officials point to Mr. Putin's nominal commitment to an eventual U.N.-supervised election with participation by all Syrians, including the half of the population displaced by the war. But because Mr. Assad would have no chance of winning a fair and free vote, it's a safe bet that neither the regime nor its backers in Tehran and Moscow will ever actually agree to it. The Pentagon has been seeking to maintain leverage over the political process by leaving U.S. troops in northeastern Syria to advise a Kurdish-Arab force that controls key oil fields. But Mr. Trump has now promised Turkish President Recep Tayyip Erdogan that he would stop U.S. arms deliveries to the Kurds — a decision that, The Post reported, appeared to take his national security team by surprise.

It could be that Mr. Putin will fail as an architect of a Syrian settlement in spite of the opposition's weakness and U.S. incoherence. Already he has had to postpone a conference he had hoped to stage in Sochi later this week to discuss constitutional proposals; the opposition said it preferred to negotiate in Geneva, while Mr. Erdogan objected to the participation of the Kurds. On Monday the Assad government postponed sending a delegation to Geneva, despite Mr. Putin's assurances that the regime would participate.

For now, however, Russia has supplanted the United States as the convening power of the Middle East's most important conflict. That Mr. Trump would welcome that development is another testament to his curious deference to the Kremlin. It is also, following the disastrous record in Syria of President Barack Obama, an acceleration of the collapse of U.S. global leadership.