The former England midfielder will make a "significant announcement" along with MLS commissioner Don Garber in Miami.
Beckham and his fellow investors will spend the next two days drumming up support for the project, including at an invitation-only reception on Tuesday night at a concert hall.
An MLS statement said: "Major League Soccer commissioner Don Garber and David Beckham will make a significant announcement impacting the Miami community. They will be joined by Miami-Dade County Mayor Carlos A. Gimenez."
Beckham was given an option to acquire an MLS franchise at a discounted rate of 25million US dollars as part of his deal when he joined the Los Angeles Galaxy.
The stadium has remained the key issue since it was confirmed the MLS and Beckham were considering Miami, with the preferred choice a 25,000-seater stadium on the waterfront.
If funding for the stadium can be agreed, Beckham's team is likely to take part in 2017.
Beckham is also expected to attend a youth football event on Wednesday afternoon after the announcement.