Panetta doesn't think they are trying to develop a warhead. However, he may be one of the few in the US and the only one of our "allies", which is who the attribution in the original article was. Furthermore, just because they aren't trying NOW, doesn't really mean much. Once they can produce the nuclear material, the rest of it is fairly well known. Developing the fuel is the whole game basically. So your concern is basically a distinction looking for a difference. Which is why Panetta's answer on CBS was relatively noncontroversial.