If there's "every reason to believe" it's the opposition forces and not the Syrian government in control of and using chemical weapons, what good does it do for the Syrian government to "place its chemical arsenal under international control"? How can these two statements be reconciled?

Putin says:

No one doubts that poison gas was used in Syria. But there is every reason to believe it was used not by the Syrian Army, but by opposition forces, to provoke intervention by their powerful foreign patrons, who would be siding with the fundamentalists.

Then later:

A new opportunity to avoid military action has emerged in the past few days. The United States, Russia and all members of the international community must take advantage of the Syrian government’s willingness to place its chemical arsenal under international control for subsequent destruction.