Unions that want to represent thousands of airport screeners are heading for a showdown with the Senate as early as Monday, with some lawmakers looking to revoke the collective-bargaining rights the Transportation Security Administration just granted them.

TSA Administrator John Pistole announced for the first time Friday that he would allow security officers to bargain over certain workplace conditions like shifts and assignments. The decision follows months of lobbying by the two unions vying to represent them -- screeners are set to vote next month on whether to unionize and, if so, with whom. In making his decision, Pistole vowed that the TSA "will not negotiate on security."

But that's exactly what some lawmakers are concerned about. They're worried that a big union presence through the TSA ranks could stifle the organization's flexibility when it needs to scramble in response to security threats. Sen. Roger Wicker, R-Miss., has introduced an amendment to a Federal Aviation Administration bill that would explicitly prohibit TSA screeners from collectively bargaining -- he's now looking for a vote on that as soon as Monday.

"The Obama administration's actions today to move forward on unionizing our TSA workforce with collective bargaining rights could hamper our national security," Wicker said in a statement, slamming the administration for approving the "ill-advised policy" while the Senate was considering it.

Sen. Jim DeMint, R-S.C., who has previously described TSA unionization as a "homeland security disaster," said the decision would benefit "union bosses and Democratic Party coffers" at the expense of American security. DeMint said the collective-bargaining rights could interfere with "minute-by-minute security decisions," forecasting an environment where union bosses have to approve vital changes.

"The Senate has the ability to reverse this political decision and put security first," he said, rallying support for Wicker's amendment.

But supporters of TSA unionization say these warnings simply are not realistic. For starters, TSA screeners would be prohibited from striking, just like other federal employees. The TSA says they would also be barred from "engaging in work slowdowns of any kind."

Under Pistole's plan, the unions would not be able to negotiate on security policies, pay, job qualifications or disciplinary standards, according to the TSA.

Sen. Joe Lieberman, I-Conn., who supports giving the workers union rights, said Pistole's announcement marks a step toward "higher job performance and, therefore, better security for our nation."

The National Treasury Employees Union is calling on senators to vote against the Wicker amendment. According to Aviation Online Magazine, the union sent a letter Thursday to every U.S. senator in opposition to the proposal.

"This decision and the upcoming representation election at TSA will give these officers a voice in their workplace and a chance at a better future," NTEU President Colleen Kelley said in a statement, adding that the traveling public will be better served by a more professional workforce.

The NTEU is competing against the American Federation of Government Employees for the right to represent the TSA's more than 40,000 officers. More than 13,000 of them already pay dues to a union, but their representation is limited and they do not enjoy collective-bargaining rights.

The decision to grant collective-bargaining rights comes after the TSA decided against expanding a program that allowed private screeners to replace government ones at select airports. Rep. John Mica, R-Fla., chairman of the Transportation and Infrastructure Committee, said the two decisions taken together are "all bad news for the traveler, the taxpayer and aviation security."