WASHINGTON (AP) — The Senate on Tuesday sustained President Barack Obama's veto of a bill that would have scrapped a new government rule on union elections.

It marked the second time that Congress has failed to override an Obama veto since Republicans took control of the House and Senate in January. The Senate fell short earlier in overriding Obama's veto of legislation calling for construction of the Keystone XL pipeline.

Proponents of the new National Labor Relations Board rules say they are modest reforms that would simplify and streamline union elections, limiting the ability of companies to drag out the certification process and buy time to fight the union.

Critics say the new rules give unions a chance to ambush employers with demands for votes on representation. Opponents say it could shorten the typical time between a union's petition for recognition from more than a month to less than two weeks.

The rule would also give unions the telephone numbers and email addresses of workers to make it easier for organizers to communicate with workers.

The new rules went into effect last month.

The vote in the Senate was 96-3, and did not reflect Republican support for the legislation that they passed over Democratic opposition. Instead, it came on a parliamentary maneuver that reflected recognition by Republicans, who have 56 seats in the 100-member Senate, that they lacked the two-thirds majority to override a veto.