At a colorful ceremony in one of Saddam Hussein's old palaces outside Baghdad, the U.S. military formally ended its combat role in Iraq and passed command of the remaining 50,000 American troops to a new four-star general.A U.S. military band played as American and Iraqi flags flew, and American and Iraqi troops and civilians filled the cavernous atrium of the Al-Faw palace to watch U.S. Vice President Joe Biden preside over the ceremony.Biden noted the sacrifice of American and Iraqi forces, and of Iraqi civilians. He noted that more than one million U.S. troops have been assigned to Iraq during the last seven-and-a-half years. And the vice-president said American involvement with Iraq will continue, not only with the thousands of troops advising its military, but with a surge of diplomats and aid workers.US vice-president Joe Biden says Iraq's political parties are close to forming a government, almost six months after the country held a general election.Iraq has been in a political vacuum since elections in early March produced no clear government. Leaders of the two rival coalitions have been in talks for months but cannot agree on how to share power. Mr Biden, who has been in Iraq to mark the end of the US combat operation, says he has met every one of the major leaders and representatives of each party that won seats in the Iraqi Parliament.