Their views collided over Washington's approach towards Syria; McCain argued passionately for arming the opposition while Moussa pressed for talks with Russia.
Other high-profile figures on the panel, like Nabil Elaraby, Head of the Arab League, and Robert Menendez, a US Senator for New Jersey, also joined the discussion, which stirred strong reactions from the audience.
"A mere deal between Russia and the US will not suffice to solve the problem," Moussa said, adding that, "Iran is part of this problem, it has to be addressed, and the Arab world has to be present."
Senator McCain remained skeptical over the prospect of fruitful peace talks, emphasizing that the Syrian regime is currently winning the war.
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"We will be at other conferences, at other times, in coming years. We will see who was right," the Senator said in a remark directed at Amr Moussa. "I am all for a conference, I am all for peace talks – nothing is better. But as long as Bashar Assad believes he can win, and he is winning right now, there is no motivation to stop the fighting."
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