A pastor and a bishop of the United Methodist Church are facing disciplinary procedures because they officiated at a same-sex wedding on Saturday.

Bishop Melvin Talbert and Pastor Val Rosenquist officiated at the service for Jim Wilborne and John Romano. However, the UMC's Book of Discipline prohibits such services in spite of repeated efforts to rewrite it.

Talbert, who is 81 and retired, is a long-time campaigner against discrimination and in 1960 spent time in a cell with Martin Luther King.

He described his stance as an act of "biblical obedience".

Speaking at First United Methodist Church in Charlotte, North Carolina, he said: "Discrimination is discrimination, no matter where it is, and it's wrong. I hope that what we did here yesterday will be an act of evangelism for people...who are looking for safe places to come because they don't want to be identified with anti-gay [sentiment]."

He told the congregation: "Your pastor could have complaints filed against her, and I could, too." He added: "But it's the right thing to do. If it costs us, if there are consequences, so let it be."

Rosenquist, the church's senior pastor, said the UMC's Book of Discipline had "institutionalised oppression and discrimination". The church voted last August that it would sanction same-sex marriages whether it violated the UMC code or not.

She said of LGBT members: "These folks are our brothers and sisters. It's just a matter of obeying our covenant with one another throughout the church, that we are to minister to all and to treat all the same. I'm just following what I was ordained to do, what I was baptised to do."

A statement for the Charlotte Observer from the office of Bishop Larry Goodpaster, who leads the Western North Carolina Conference of the United Methodist Church, said: "We are aware of the wedding at First United Methodist Church on Saturday. Bishop Goodpaster will follow the procedures in The Book of Discipline if a formal complaint is filed."

Many US-based UMC ministers and congregations are relaxed about or in favour of same-sex marriage. However, though it has around 7 million members in the US, it it is an international denomination and moves to change its rules meet strong resistance from African countries and others with a conservative tradition.

Its General Conference starting on May 10 is to consider petitions repealing prohibitions on clergy conducting same-sex marriages.