U.N. involvement would remove the onus on the U.S. to negotiate on its own.

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Syria denies it, but an ongoing U.N. investigation has found indications of Syrian involvement.

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Damascus has denied any role in Hariri's killing, but a U.N. investigation has found indications of Syrian involvement.

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As with U.S. and international involvement in Libya in 2011, a resolution from the U.N.

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