The Democratic-controlled Congress cleared legislation to begin withdrawal of US troops from Iraq by Oct. 1 with a goal of a complete pullout six months later. The White House dismissed the legislation as "dead before arrival." The 51-46 Senate vote was largely along party lines, and like passage by the House of Representatives a day earlier, it underscored that the war's congressional opponents are far short of the two-thirds majority needed to override the promised Bush veto. Democrats marked Thursday's final passage with a news conference during which they repeatedly urged Bush to reconsider his veto threat. "This bill for the first time gives the president of the United States an exit strategy" from Iraq, said Rep. David Obey. The White House was unmoved. "The president's determined to win in Iraq. I think the bill that they sent us today is mission defeated," said deputy press secretary Dana Perino. "This bill is dead before arrival."