CHATTANOOGA (AP) — Three Democratic U.S. senators are expressing concerns about delays to an election over whether Volkswagen maintenance and production workers in Tennessee should unionize.

Sens. Sherrod Brown of Ohio and Gary Peters and Debbie Stabenow of Michigan sent Volkswagen Group of America CEO Scott Keogh a letter Tuesday.

It says any election delays further enable anti-union campaigns to target and intimidate workers.

Volkswagen says it's neutral on the possible Chattanooga unionization, respects the right to decide representation and will respond to the letter.

The senators question Volkswagen's neutrality, saying they've heard Chattanooga supervisors are having anti-union conversations with workers.

Earlier this month, the National Labor Relations Board indefinitely delayed election procedures in Chattanooga at Volkswagen's request.

The union, UAW International, argues Volkswagen is using legal games to obstruct Chattanooga workers' rights.