Former U.S. hostage negotiator: The Iranians are tougher negotiators than the Russians, the Chinese, and even the Taliban

<p>Former U.S. hostage negotiator Roger Carstens warns that the Iranians are tougher negotiators than the Russians, the Chinese, and even the Taliban. He says the Iranians often move the goal posts and that "you never really quite get to the end state until the very end." </p>