I think continued actions by Bashar al-Assad clearly call into any question of him expecting to have any legitimacy to continue as the leader of Syria. With each of those actions, like attack with conventional weapons, barrel bombs and block humanitarian aid he really undermines his own legitimacy.

We are making tremendous progress that ISIS really does present to the homeland and to other homelands of allies around the world.

Russia and the USA are two largest nuclear powers in the world; it's a really important relationship. How do we start making this work? How do we live with one another? How do we work with one another? We simply have to find a way to go forward.

As far as I know, the line of communication between the U.S. and Russia continues to be open and the battlefield commanders are able to communicate with one another. I am aware that there have been certain public statements made out of Moscow.

I think the relationship between the USA and Russia is too important. And it's too important to not find a way to move forward.

We're hopeful that Russia will choose to play a constructive role in supporting ceasefires through their own Astana talks, but also, ultimately, through Geneva. And if we can achieve ceasefires in zones of stabilization in Syria, then I believe we will have the conditions to begin a useful political process.

I think the Russians need to think more carefully about the commitment they made under the chemical weapons agreements to be the guarantor that these weapons would be seized, they would be removed, they would be destroyed. And since they are Bashar al-Assad's ally, they would have the closest insight as to the compliance.