NAJAF, Iraq (CNN) -- A prominent aide to renegade Shiite Muslim cleric Muqtada al-Sadr was arrested early Wednesday in Najaf, according to U.S. military officials and a representative of al-Sadr's office.

CNN: Iraqi cleric's aide arrested in Najaf

Iran is the chief regional ally of Syrian President Bashar Assad and is considered close to Iraq's Shiite Muslim-dominated government.

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Al-Mawla, a Shiite Muslim, was a senior officer in Saddam Hussein's army and is now a high-ranking member of Iraq's national reconciliation committee.

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Rumsfeld is expected to meet with Jawad al-Maliki, the Shiite Muslim politician recently tapped as Iraq's prime minister.

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He cited the latest political developments, the filling of top posts in the new government and the designation of Shiite Muslim politician Nuri al-Maliki as prime minister.

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The manifestations of this rising tide have become evident not only in the Muslim world - Arab and Persian, Sunni and Shiite alike.

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Sunni-Shiite rivalries -- not only in Iraq, but throughout the Muslim world -- have been a factor in the torpid pace of diplomatic relations between Iraq and the Arab world.

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The oil-rich gulf kingdom, a Sunni Muslim country with deep suspicion of Iran's Shiite Muslim rulers, is believed to also be adamantly opposed to any deal that would benefit Iran.

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U.S. and British fliers also enforce a ban on Iraqi aircraft in the "no-fly" zones over northern and southern Iraq, established to protect Kurdish and Shiite Muslim minority populations after the Gulf War.

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