Jason Terry reached a verbal agreement Tuesday on a three-year, $15 million free agent contract with the Celtics.

The Mavericks are unlikely to match the Celtics’ offer to Terry.

“What Jet did for this city and franchise will never be forgotten,’’ Mavericks president of basketball operations Donnie Nelson said in a statement. “He’s one of the greatest clutch performers in the history of our game and an even better person.

“We wish him nothing but the very best. Unfortunately, we cannot jeopardize our flexibility at this time.’’