Did Putin just 'smelled' the Western trap?
The Russian president was probably waiting for the beginning of the negotiations, in order to identify the real intentions of the Westerners and the alleged Syrian opposition. It appears that they were only interested to gain some time, so that to re-organize their forces, not to achieve a solid agreement which would attempt to put an end to the Syrian mess.
If this is true, then we are talking about a surprise move by Putin against the plans of the Westerners to trap him into a dead end war, opening other fronts too, in order to get rid of him.
Of course, there is always a possibility that Russians and Americans have already agreed to re-build the map of the Middle East, which will include a sovereign Kurdish state. This explains Erdogan's anxiety who acts under pressure and makes things worse, as he probably understands that he has been left out of the game.
http://failedevolution.blogspot.gr/2016/03/did-putin-just-smelled-western-trap.html