WASHINGTON, Jan. 5 (Xinhua) -- The Pentagon announced on Friday changes of several key military leadership posts related to Iraq, including replacing the top commander of U.S. forces in Iraq George Casey.

    In a statement, Defense Secretary Robert Gates said Casey will be elevated to the post of Army Chief of Staff and his Iraq job will go to Lt. Gen. David H. Petraeus, commander of the Army's Combined Arms Center in Fort Leavenworth.

    Petraeus gained fame for his early success in training Iraqi troops and securing a volatile city in northern Iraq.

    Gates also nominated Navy Adm. William J. Fallon to head the Central Command, replacing Gen. John P. Abizaid as the top U.S. military commander for the Middle East.

    Both Abizaid and Peter Schoomaker, the current Army Chief of Staff, will retire.

    "We are engaged in three wars -- in Iraq, Afghanistan, and against jihadist terrorism worldwide.... I firmly believe that Generals Petraeus and Casey and Admiral Fallon, as individuals and as a team, bring to the challenges that face us the qualities necessary to be successful in war and to protect the American people," Gates said in the statement.

    The new nominations must be confirmed by the Senate.

    The military reshuffle is part of the Bush's administration's ongoing shakeup of top officials on Iraq.

    U.S. media said the real reason of Casey's departure from Iraq is that he is at odds with President George W. Bush on the military strategy in Iraq.