The Republican-controlled Senate Wednesday voted 53-46 to kill a National Labor Relations Board rule reducing the time between a union's request for representation and a vote by workers on it.

The legislation now goes to the House, where approval is also assured.

But President Barack Obama has threatened to veto the measure, and the Senate's vote indicates that supporters are far from the two-thirds majority that would be needed to override him.

The AFL-CIO has praised the rule. Senate critics say it would permit what they call ambush elections that limit the ability of businesses to defeat certification elections. Bill sponsor Lamar Alexander says the rule would shorten the time between a union petition and a representation election from the current median of 38 days to as few as 11 days. Labor organizers, however, may take as long as they like building support for the union before petitioning for an election.

"This is why we call it the `ambush election' rule -- because if this rule goes into effect, after a union has had months to build its case in its favor, a business will only have a few days to respond," said Sen. Mike Enzi, R-Wyo. "That is only a few days to figure out what union officials have told employees to determine if there are any misstatements, falsehoods or misconceptions."

The Obama administration and its Democratic allies say the new rules are modest reforms that would simplify and streamline union elections and limit the ability of companies to drag the certification process out and gain time to fight a union's bid to win a certification election.

"Workers deserve the right to organize without needless delays of months or even years before they get to cast a vote," said Sen. Edward Markey, D-Mass. "They deserve a union election process that cannot be manipulated to gain unfair advantage. They deserve a process that is clear and efficient, not one that is bogged down with time-consuming, needless bureaucratic procedures."

Sen. Lisa Murkowski of Alaska was the sole Republican to oppose the measure to overturn the new rules.

The new rule would also give unions the email addresses and telephone numbers of workers to more easily communicate with them in advance of a vote.

The Senate vote took place under a rarely used law that limits debate on congressional attempts to reject agency rules, and bars opponents from stalling a final vote.

The rule is scheduled to take effect in April.