White House on Defensive After Bremer Talk WASHINGTON - The White House staunchly defended its Iraq policy Tuesday as new questions emerged about President Bush's prewar decisions and postwar planning: An impending weapons report undercut the administration's main rationale for the war, and the former head of the American occupation said the United States had too few troops in Iraq after the invasion.    Four weeks before Election Day, Democrat John Kerry pounced on the acknowledgment by former Iraq administrator Paul Bremer that the United States had "paid a big price" for insufficient troop levels...