A Roman Catholic nun was excommunicated and dismissed from her religious order last week after admitting that she was secretly ordained as a priest earlier this year.

Sister Leticia Rawles, 67, was ordained in April by the Association of Roman Catholic Women Priests and has since presided over religious services.

Currently critically ill in hospital, Rawes said she wanted to fulfil a call to priesthood she had since childhood and be ordained before it was too late.

"I thought that before I die, I want to fulfil God's call and my life-long dream to become a priest," Rawles said in a statement on Tuesday.

The Roman Catholic Church is unequivocal in its position on women's ordination, and the automatic consequence is excommunication from the Church, thus under church law Rawles was excommunicated in April.

Sister Joyce Lehman, president of Rawles' order the Sisters of the Precious Blood, told Cincinnati.com they had no choice but to dismiss Rawles.

"She has gone against what the Catholic Church teaches," Lehman said. "We didn't make a big decision to do this. She was dismissed as a result of her actions."

Supporters of Rawles' ordination have appealed to the Vatican to remain with the Dayton, Ohio-based Sisters of the Precious Blood. They said she has served the church for decades and should be able to remain a nun even if they do not recognise her as a priest.

"Here's a woman who has devoted 47 years of her life in service to the people of God," said Janice Sevre-Duszynska, spokeswoman for the Association of Roman Catholic Women Priests. "And now she's being thrown out of her community."

Despite the Vatican's position on the ordination of women showing no signs of changing, there is a growing movement of women seeking ordination. Sevre-Duszynska said that 77 women have been ordained through their two year programme and around 220 have been ordained worldwide.

Lehman said she and other members of Sisters of the Precious Blood had been shocked to discover Rawles had secretly been studying for two years and been ordained.

"She kept it secret from us," Lehman said. "There's no way she didn't know the consequences. This isn't something that should have been a surprise to her."

Although she faces dismissal, the order will ensure Rawles continues to receive medical care and housing.

"We are in the process of setting up some means of financial support," Lehman said. "Not because she was in the order, but because she is a person in need."