The former England captain's contract with the MLS allowed him to buy into the league once his playing career was over, but that deal does not extend to Thierry Henry's side
Beckham will leave the United States after playing for LA Galaxy in the MLS Cup this weekend, and has hinted he will return to the league once his playing days come to an end.
However, Garber has stated that the 37-year-old will not be able to invest in either the New York Cosmos, who are attempting to relaunch themselves, nor New York Red Bulls, who are not for sale in any case.
"Anything's a possibility other than his right to exercise that option in New York," Garber told reporters.
"Major League Soccer has been looking at the possibility of expanding in New York since the league was founded in '96.
"There was a concept of having two teams in the league way back then. We knew when we were speaking with David and [Beckham's agent] Simon Fuller that eventually we would have an opportunity in New York regardless of the role that David played in helping grow the league."
Garber also hailed Beckham's impact on football in the United States, but insisted that the MLS has now gained enough credibility to thrive without the former England captain playing there.
He added: "We needed David Beckham in 2007 to help drive our credibility, to help grow our popularity and to show the world really that the United States... was ready to support a division one league.
"We don't need anything today to get us to the next level. I have no regrets whatsoever in any aspect of this deal."
The MLS supremo went on to say that he believes another player "will surprise the soccer world" like Beckham did by joining MLS, and that the 37-year-old and Thierry Henry have proven instrumental in luring other Designated Players to the league.