The governing body of the Church in Wales will hold a vote on whether women priests should be allowed to become bishops.
The Church in Wales' governing body has narrowly rejected proposals to allow women priests to become bishops.
The controversial bill, which has been proposed by six diocesan bishops, will be looked at by 140 members at a meeting in Lampeter.
The controversial bill was defeated by three votes at the 140-member body meeting in Lampeter, despite being backed by the Archbishop of Wales.
The Archbishop of Wales has backed the idea and said he cannot see how the church can logically exclude women.
Dr Barry Morgan had said he could not see how the church could logically exclude women from becoming bishops.
If it succeeds, England will the only UK region not to have female bishops.
However, more than 100 clergy warned in December last year they would not accept the ministry of women bishops.
If the vote is passed by a two-thirds majority in each section of the governing body, the change in Wales would come into affect immediately.
The bill, proposed by six diocesan bishops, needed a two-thirds majority in each section of the governing body to take effect.
The Archbishop of Wales, Dr Barry Morgan, said he will be voting in favour of the bill.
Its defeat leaves Wales and England as the only UK regions in the Anglican Church that do not have female bishops.
He said: "I do not personally see how having agreed to ordaining women to both the diaconate and priesthood the church can logically exclude women from the episcopate."
The Right Reverend John Stewart Davies, Bishop of St Asaph, is also supporting the bill.
He said: "The most compelling reason for bringing forward the bill is that we should be able to widen the field of potential candidates.
"Women are making a major contribution to our ordained ministry in almost every area of church life.
"There's an enormous amount of talent out there and why should they not be included as potential candidates for bishops? That's the heart of the matter."
Opposition
But last December more than 100 clergy from the Church in Wales signed a letter published in the Church Times warning they would not accept the ministry of women bishops.
The Reverend Roy Doxsey, of St German's Church in Cardiff, is against the bill.
He said: "The bishops are in the apostolic succession and while our Lord had hundreds of disciples, amongst them many, many women, out of those hundreds of disciples he only selected 12 and they were all male."
Others opposing the bill question whether it was right to change something which is part of tradition.
Women have been ordained as priests within the church in Wales since January 1997.
Women have been ordained as priests within the church in Wales since January 1997.
The vote will be take place at the University of Wales, Lampeter.
Speaking ahead of the vote on Wednesday, Dr Morgan, said: "I do not personally see how having agreed to ordaining women to both the diaconate and priesthood the church can logically exclude women from the episcopate."
The Rt Rev John Stewart Davies, Bishop of St Asaph, had also supported the bill.
But clergy opposed to the change signed a letter published in the Church Times last December warning they would not accept the ministry of women bishops.
Among those opposing the bill was the Rev Roy Doxsey, of St German's Church in Cardiff.
Speaking ahead of the vote, he said: "The bishops are in the apostolic succession and while our Lord had hundreds of disciples, amongst them many, many women, out of those hundreds of disciples he only selected 12 and they were all male."
