The nation's largest federal employee union is moving ahead with efforts to represent about 40,000 airport screeners even though the government has not given them collective bargaining rights.

The American Federation of Government Employees says it wants to be ready to begin contract negotiations as soon as the bargaining rights are granted.

Workers at the Transportation Security Administration have tried for years to win the same union protections as other federal employees. Republican opponents claim that could jeopardize national security.

President Barack Obama has promised to get the screeners collective bargaining rights. But Obama's choice to lead the agency withdrew his name last month, saying his nomination had become a lightning rod for criticism from those with a political agenda.