WASHINGTON – The Senate narrowly rejected a measure to restore more than $1 billion in funding for Amtrak on Wednesday, upholding President Bush’s plan to force the struggling rail line into bankruptcy and restructuring.

Most Democrats and four Republicans – including Olympia Snowe and Susan Collins of Maine – urged continued federal sponsorship, arguing that urban and rural travelers across the country, and especially in poor areas, rely heavily on the train service.

The 52-46 vote against the funding represented a setback for Amtrak supporters, who hoped a favorable vote in the Senate would cripple Bush’s plan to “zero-out” Amtrak’s operating budget.

“Certainly zero is not an option because zero only leads to bankruptcy and bankruptcy is not the proper solution,” said John Robert Smith, the mayor of Meridian, Miss., and a former Amtrak chairman who was speaking on behalf of the U.S. Conference of Mayors.

Bush administration officials have argued that the federal government must stop subsidizing passenger rail service and force Amtrak to shut down little-used routes.