John Kerry: "We absolutely agree that ISIL/Daesh and al-Nusra are absolutely outside this process, no matter what...With regard to the announcement or proclamations of the people who came together in Riyadh [that Assad must go now], that is not the position of the International Syria Support Group, it is not the basis of the Geneva communiqué, it is not the basis of the UN resolutions; and we are assured by the members of the International Syria Support Group who were attending that meeting, and helping at that meeting, and hosting that meeting, that that is not in fact the starting position, because it's a non-starting position, obviously."
Kerry thinks he has successfully bullied the states opposed to Assad and the Syrian opposition into accepting a deal the Russians can live with. You could get people to reject al-Nusra, you can insist that Assad is staying, but you can't do both. For more on the US' double-dealing, see here.*