Can an employer elect not to withhold fica-ss & mm if the employer provides a retirement account for its employees and those employees participate?

can an employer elect not to withhold fica-ss & mm if the employer provides a retirement account for its employees and those employees participate?
I don't think so, unless the employer is say a church and the employee is a minister, it's a one time, no going back type option for ministers, once they elect not to have fica withheld, I don't think they can later opt into the social security system and they are on their own when it comes to retirement or death or disabilty. Some municipalities, fire fighting districts and similar entities can elect not to participate in the soc security system and thus their employees don't have fica, ss withheld. Anyone out their wish to correct me or add something please do so.

Thanks. I think that you are right; after posting, I did some research about it; be blessed.:)