The largest labor groups are urging senators to oppose a rules-of-the-road crypto bill scheduled to have an initial vote on Thursday.

In a letter and email first seen by CNBC, the AFL-CIO, as well as the Service Employees International Union, American Federation of Teachers, National Education Association, and the American Federation of State, County and Municipal Employees warned senators that the bill could jeopardize retirement accounts for millions of workers.

The push from unions comes ahead of the Senate Banking Committee’s vote on the crypto bill scheduled for Thursday. Despite Democrats working with Republicans on the bill over the last few months, it is not clear if any Democrats will…