MOSCOW — The fifth trilateral meeting today between the leaders of the guarantor states of the Astana process on the settlement in Syria could have been just another routine gathering of three of “today’s friends — centuries-old adversaries” if it were not for the complications that have emerged since the previous such meeting in Sochi on Feb. 14.

The smoldering tensions between Russia and Iran that overshadowed that encounter now have given full way to the Moscow-Ankara rift over Idlib. Putin was unwilling to come unprotected from all sides, so a day before he landed in Ankara the Russian Defense Ministry announced that Moscow had completed the second stage of S-400 deliveries to Turkey as a sign of being serious about its commitments to the agreements with Ankara. Meanwhile, Russia’s feelings about Turkey’s implementation of its own commitments remain sour.

“We are managing the cease-fire in the province, but that does not mean we have to accept the presence of terrorist groups in Idlib. This is why I suggest examining practical steps that Russia, Turkey and Iran might take together to eradicate the terrorist stronghold completely,” Putin said seven months ago.

Now the tone has changed, and so has the Russian military strategy on returning Idlib to Syrian government control. Prior to the trilateral meeting, Putin had separate talks with both Erdogan and Rouhani in the company of their ministers and advisers. The talks between the Russian and the Turkish delegation were scheduled to last for an hour but continued for over two hours and both presidents looked exhausted and visibly irritated when they finally came out of the meeting room.