The Mets are planning to open their gates for free to fans for a March 18 intra-squad game at Clove Park in Port St. Lucie, Fla., The Post has learned.

This remains in the planning stage because there were still ongoing attempts by the Mets to add an official spring training game, or “B” game against an opponent on that date. As of Friday morning, scheduling spring training games remained a fluid matter throughout the sport.

But if the intra-squad game comes off on the 18th, it would come a day before the Mets begin their official spring training schedule against the Nationals.

The Mets have two intentions with the intra-squad game. First, with a shortened spring training, they are looking to add as many game situations as possible. They are discussing, for example, using the off-days in the spring schedule as a voluntary camp day for anyone who wants to participate in what could be “B” games vs opponents or more intra-squad games.

Second, the Mets see an opportunity for a goodwill gesture toward fans who could be upset at the lockout that shortened spring training.