Labor leaders say unionizing Transportation Security Administration (TSA) screeners would strengthen security by improving working conditions and reducing high attrition and injury rates, which cause staffing shortages.
TSA leaders say security would suffer because the agency could not quickly reassign screeners to counter new threats.
President Bush might veto any bill that would let TSA screeners unionize. Spokesman Scott Stanzel said senior Bush advisers in the White House and Homeland Security Department, which oversees the TSA, would recommend a veto of such a bill.
A White House statement expressed strong opposition to union rights for screeners, saying unionization could jeopardize the agency's ability to give screeners new assignments.
Thirty-six Republican senators signed a letter Tuesday saying they would support a presidential veto. That's enough senators to uphold a veto.
The showdown comes as the Senate begins debate on proposals to improve aviation and rail security and terrorism prevention by enacting some recommendations of the 9/11 Commission.
Democrats who control the Senate want to pass a broad anti-terrorism bill in coming weeks that includes a provision that would allow the nation's 43,000 airport screeners union representation.
The Democratic-controlled House of Representatives included an identical provision in a 277-page homeland security bill that passed last month. The 9/11 Commission did not address unionization.
Screeners have been barred from collective bargaining since the TSA was created shortly after 9/11.
Most civilian federal employees can be represented by a union, and many TSA sister agencies in the Homeland Security Department have unions.
TSA Administrator Kip Hawley said he would lose flexibility if he needed union approval before changing screener duties or if he had to fight a union to fire a negligent screener. "If we want to bring in new (security) equipment or move equipment, that's subject to negotiation and delay," Hawley said.
Hawley said unionization would cost the agency $160 million to hire labor lawyers and set up collective bargaining.
The nation's largest federal labor union says the TSA's scenario is a misleading scare tactic. A union would not block security procedures or training requirements but would ensure they were implemented fairly, said Mark Roth, a lawyer for the 600,000-member American Federation of Government Employees, which wants to represent screeners. "They can change screener duties, but we can make sure people get a fair opportunity to be trained to meet new qualifications," Roth said.
Roth said union representation could improve morale and reduce TSA injury and turnover rates, which are among the highest in the federal government.
Federal labor unions negotiate working conditions and are generally barred from negotiating pay and benefits, which are set by law. Federal law allows agencies to "take whatever actions may be necessary to carry out the agency mission during emergency."