But Lanza sees his work as more than a challenge, or a call to arms.

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On the most immediate challenge, working out an arms control agreement to replace the START I treaty which expires December 5, the two presidents signed a joint understanding for a follow-on agreement to START that commits both parties to a legally binding treaty that will reduce nuclear weapons.

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Many of the states that would have to enforce a small-arms accord are too weak (partly because of the challenge they face from armed rebels or criminals) to do so.

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In each case, the main challenge for the Treasury is political to nudge the other arms of government gently in the desired direction, and in any event take the credit if things go well.

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Together, these two strategic arms are raising the stakes of Iran's challenge to its neighbors and to the West to unprecedented and unacceptable heights.

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Sectarianism aside, the large number of militia groups that have taken up arms across Syria will present a "significant challenge" to the country's future stability whoever ends up in power, Joshi said.

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