NEW YORK — Michael Vick is back in the NFL. Now all he needs is a team to play for.

Vick, free after serving 18 months in prison for running a dogfighting ring, was reinstated with conditions by NFL commissioner Roger Goodell on Monday. He could participate in regular-season games as early as October.

Vick can immediately take part in preseason practices, workouts and meetings and can play in the final two preseason games — if he can find a team that will sign him. A number of teams have already said they would not.

Once the season begins, Vick may participate in all team activities except games, and Goodell said he would consider Vick for full reinstatement by Week 6 (Oct. 18-19) at the latest.

Goodell suspended Vick indefinitely in August 2007 after the former Atlanta Falcons quarterback admitted bankrolling a dogfighting operation on his property in Virginia. At the time, Goodell said Vick must show remorse before he would consider reinstating him.

‘‘I accept that you are sincere when you say that you want to, and will, turn your life around, and that you intend to be a positive role model for others,’’ Goodell said in his letter to Vick. ‘‘I am prepared to offer you that opportunity. Whether you succeed is entirely in your hands.’’

‘‘Needless to say, your margin for error is extremely limited,’’ the letter said. ‘‘I urge you to take full advantage of the resources available to support you and to dedicate yourself to rebuilding your life and your career. If you do this, the NFL will support you.’’

Goodell said he spoke to numerous current and former players and coaches as he weighed his decision and that the responses were ‘‘very mixed.’’

‘‘I do recognize that some will never forgive him for what he did,’’ Goodell said. ‘‘I hope that the public will have a chance to understand his position as I have.’’

Vick, once the highest-paid player in the league, said he was grateful for a second chance.

‘‘I would like to express my sincere gratitude and appreciation to commissioner Goodell for allowing me to be readmitted to the National Football League,’’ Vick said in a statement released by his agent, Joel Segal. ‘‘I fully understand that playing football in the NFL is a privilege, not a right, and I am truly thankful for the opportunity I have been given.

‘‘As you can imagine, the last two years have given me time to re-evaluate my life, mature as an individual and fully understand the terrible mistakes I have made in the past and what type of life I must lead moving forward,’’ he said.

The announcement came after a busy first week of freedom for Vick, who met with union leaders and Goodell on consecutive days last week. His 23-month federal sentence ended when an electronic monitor was removed from his ankle on July 20 at his home in Hampton, Va.