I doubt he said that because it's what he thinks the US wants to hear. I would imagine he is deeply concerned about Iran creating a destablising influence in the region. You are right about saying something different in public to his subjects though, as such a view would be hugely controversial in the Arab world and a major embarrassment to the king. It seems he wanted the US to strike against the Iranian uranium enrishment program:

http://www.reuters.com/article/idUSTRE6AP06Z20101128