CAPITOL HILL (AP) -- Congress is headed toward a historic veto showdown with President Bush on the Iraq war.

A defiant Democratic-controlled Senate has passed legislation that would require the start of troop withdrawals by October first.

The 51-to-46 vote was largely along party lines. Like House passage of the same bill a day earlier, it fell far short of the two-thirds margin needed to overturn the president's expected veto.

Nevertheless, the legislation is the first binding challenge on the war that Democrats have managed to send to Bush since they reclaimed control of both houses of Congress in January.

The $124 billion funding bill requires troop withdrawals to begin October first, or sooner if the Iraqi government does not meet certain benchmarks. The House passed the measure yesterday by a 218-to-208 vote.

UPDATE: White House declares measure 'dead on arrival'

WASHINGTON (AP) -- In an bold wartime challenge to President Bush, the Democratic-controlled Congress has voted to begin withdrawing US troops from Iraq by October first with a goal of a complete pullout six months later.

The White House is dismissing the legislation as "dead before arrival."

The 51-to-46 vote in the Senate was largely along party lines. Like House passage a day earlier, it underscored that the war's opponents are far short of the two-thirds majority needed to override a Bush veto.

Democrats held a news conference to repeatedly urge Bush to reconsider his veto threat. Senate Majority Leader Harry Reid said the legislation is "in keeping with what the American people want."

White House spokeswoman Dana Perino says "the president is determined to win in Iraq."

The bill would provide $124 billion, most of which would go for the wars in Iraq and Afghanistan.