Episcopalians are prepared to greet a historic yet controversial occasion – the ordination of the first openly lesbian bishop on Saturday.

The Diocese of Los Angeles will be ordaining its first two women bishops at the Long Beach Arena. But much of the attention is on the Rev Mary Douglas Glasspool, whose consecration could further impair relationships with the rest of the global Anglican Communion.

"We elected her (Glasspool), not only a woman but a woman who is who she is fully as a lesbian person," said Los Angeles Bishop the Rt Rev J Jon Bruno in a video message.

Glasspool, who has been with her lesbian partner since 1988, was elected in December to the office of bishop suffragan in the Diocese of Los Angeles. She received the required majority of consents from the wider church and the OK from the presiding bishop's office in March.

This weekend, she will become the second partnered homosexual bishop in The Episcopal Church, after V Gene Robinson of New Hampshire who was consecrated in 2003.

"We rejoice as we enter a whole new era into the 21st century, rethinking, relooking and reforming who we are as Christian people in the world," said Canon Randy Kimmler, missioner for vocations in the Los Angeles diocese. "This is like a big first step for us so we rejoice in this."

Many in the 77 million-member communion, however, are grieving. Bishops, mainly from the Global South, say Glasspool's ordination shows that US Episcopalians are continuing to go against Scripture and defy the wishes of the wider body.

The Anglican Communion had called for gracious restraint in regards to the ordination of partnered gays and the blessing of same-sex unions.

Dr Peter Jensen, the Archbishop of Sydney, said many Anglican provinces have given up on The Episcopal Church – the US arm of Anglicanism – and regard themselves as "out of communion" with them, according to the Church of England newspaper.

"They renew the call for repentance but can see that, failing something like the Great Awakening, it will not occur," he said.

Last month, some 130 Anglicans from 20 provinces endorsed a document encouraging one another to reconsider their relationships with The Episcopal Church and condemning the western church body for pursuing "an agenda of their own desire in opposition to historic norms of faith, teaching and practice".

"Some of our Provinces are already in a state of broken and impaired Communion with The Episcopal Church USA and the Anglican Church of Canada. Their continued refusal to honor the many requests made of them ... have brought discredit to our witness," the document states.

Episcopal Presiding Bishop Katharine Jefferts Schori told Newsweek last month that ordaining Glasspool is not an act of defiance. Rather, "people have made their decision carefully, with abundant consideration for impact on others but also out of a sense that they deeply feel is correct," she said.

Jefferts Schori, the first woman to serve as head of The Episcopal Church, is scheduled to ordain Glasspool and Diane Jardine Bruce on Saturday.

"We'll see the first female presiding bishop enter the arena to ordain the first two women bishops of the Diocese of Los Angeles," said Bruno. "It's history-making."