But Trump's airstrike last week on a Syrian airbase
, followed by tough language from his top diplomats regarding Russia's support of the Syrian regime, suggests that Putin's options in Syria -- where he very recently was thought to hold all the cards -- are rather more limited than many previously thought.
Over the weekend, Secretary of State Rex Tillerson said that he hopes
"Russia is thinking carefully about its continued alliance with Bashar al-Assad," while Trump's ambassador to the United Nations Nikki Haley has said that the US is "calling out" Russia and Iran in the aftermath of last week's chemical attack in Idlib.
In relation to Syria -- and perhaps more importantly, Ukraine -- any dreams Russia have had of brokering a grand bargain with the US are likely over. Moscow will now have to revisit its options on how, or whether, it cooperates with the US -- and these options are not as promising as is sometimes assumed.
Much will obviously depend on how US policy develops in Syria. But it's hard to see exactly what Russia can do next without making a bad situation worse.
A direct Russian military response to America's reestablishment of itself as a factor in Syria's internal conflict is hard to imagine.
US cruise missile attacks would be hard to prevent. Russian attacks on US ships would be dangerous -- very dangerous. And publicly admitted deployment of significant numbers of Russian troops to Syria would not only be risky, but would also further lock the Kremlin into its commitment to Assad.
Abandoning Assad would also be hard for Putin. Backing a potential successor, if one were available from within the same faction, might preserve the Russia-Iran working alliance, but would be unlikely to improve the chances of an official Syrian government establishing a good measure of control over the country as a whole.
And part of Putin's argument for intervention rested on the need to support what he saw as Syria's legitimate government, probably coupled with a sense of a wider imperative to act decisively to prevent "color revolutions".
Other options for a Syrian settlement would entail a radical rethink of Russia's strategy. Working with western and different regional powers towards a post-Assad settlement would not just be unpalatable for Putin, but as the war rolls on, it also becomes increasingly complicated.
The conflict -- or more accurately conflicts -- within and around Syria has intensified the hatreds inherent in civil war. It has been a force driving extremism -- not desire for a settlement.
The Kremlin may once have thought that an imposed Alawite victory was within its sights, and may even still think that this is possible. But Putin can no longer believe, if he once did, that this can be achieved with American or possibly even European acceptance of it as being inevitable.
He must also understand that the chances of US and European sanctions for Russia's seizure of Crimea and invasion of eastern Ukraine being eased in the near future have been further reduced. Syria and Ukraine are not formally linked, but Russian policies towards both reflect the Kremlin's conviction that its use of force is its prerogative as one of the world's great powers.
Lastly, while the Kremlin may feel itself to be condemned, at least for now, to stick to its current course or something very like it, Putin and his colleagues must also take into account the fact that the Russian domestic appetite for foreign adventures is dulling.
Despite for some time looking like the only player in the game when it came to ending the Syrian conflict, Putin's long-term support of Assad has left him with very few options, none of which are simple.