PHILADELPHIA — A United Methodist pastor vowed to defy a religious order to surrender his credentials for performing a same-sex wedding, saying church officials will have to defrock him if they want him out of the ministry.

The Rev. Frank Schaefer has been told to give up his pulpit in central Pennsylvania by today if he cannot support the denomination’s Book of Discipline. But Schaefer, who describes the book as contradictory and biased against gay people, said he will not go quietly.

“I am actively committing to having those discriminatory laws changed and banished from our Book of Discipline,” Schaefer said. “That’s the only way I can reconcile being a United Methodist at this point.”

Schaefer is serving a 30-day suspension for officiating the 2007 wedding of his gay son in Massachusetts, where same-sex unions are legal. Although the Methodist church accepts gay and lesbian members, it rejects the practice of homosexuality as “incompatible with Christian teaching.”

Jurors who convicted Schaefer in a church trial last month said he should use the suspension time to decide whether he could follow church doctrine. They ordered him to resign from the clergy if he could not.

Schaefer gave his answer publicly Monday during a news conference at Arch Street United Methodist Church in Philadelphia, surrounded by dozens of sympathetic ministers and laity.