Baseball's new basic agreement permits the National League to expand by two teams to match the American League's 14 clubs, management and union officials said today.

But the expansion clause does not mandate adding any teams nor does it limit the expansion to just two teams during the life of the five-year agreement, said Lee MacPhail, president of the owners' Player Relations Committee. He explained that should the league want to add two clubs, no further management-union negotiations would be required.

"Basically, what it says is that the clubs have the right to expand and set their own ground rules, providing they followed the pattern used in the past," MacPhail said. "There's no limit on it; it's just that we have a green light for two. Anything beyond two, we have to talk to them about terms and conditions."

"It's quite similar to a provision in the last basic agreement," said Lauren Rich, assistant general counsel to the players union.

At least a dozen cities want expansion teams. They include Washington, Miami, New Orleans, Indianapolis, Denver, Phoenix, Tampa, Fla., St. Petersburg, Fla., East Rutherford, N.J., and Vancouver.

A year ago, the owners' long-range planning committee said it might expand by six teams by 1990.

The Major League Players Association asked management to commit to expansion during the life of the agreement, but MacPhail said management could not do that.

"Our answer to that was . . . that we have to consider our economic problems and get them straightened out before we expand," he said. "We asked that we have the right to expand without having to come back and negotiate a lot of financial conditions with them."