Boston's cardinal is to boycott a Jesuit college's graduation where Taoiseach Enda Kenny is the commencement speaker, over his support for abortion laws. The bill allows abortion if a doctor authorises it to save a woman's life, but opponents say it would lead to widespread abortion by also permitting it if a woman threatened suicide.
In a statement, Cardinal Sean O'Malley said abortion was "a crime against humanity" and the US Conference of Catholic Bishops has asked Catholic institutions not to honour those who promote it.
Mr Kenny is due to receive an honorary degree from Boston College at the May 20 commencement. Cardinal O'Malley said that since the college had not withdrawn its invitation and Mr Kenny had not declined it, "I shall not attend the graduation".
"It is my ardent hope that Boston College will work to redress the confusion, disappointment and harm caused by not adhering to the bishops' directives," he said.
College spokesman Jack Dunn said the school respected Cardinal O'Malley and regretted his decision not to attend graduation.
"However, we look forward to our commencement and to Prime Minister Kenny's remarks," he added. Mr Dunn said Mr Kenny was invited to because of Ireland's historically close relationship with the college and that the school "supports the church's commitment to the life of the unborn".
Mr Kenny maintains the bill affirms, rather than weakens, Ireland's general ban on abortion. "Our aim is to protect the lives of women and their unborn babies by clarifying the circumstances in which doctors can intervene where a woman's life is at risk," he said in a May 1 speech.
Last year, another Catholic college in Massachusetts was involved in a similar controversy after the Bishop of Worcester pressured Anna Maria College in Paxton to withdraw an invitation to US senator Edward Kennedy's widow, Victoria Reggie Kennedy, to deliver its commencement address.
Bishop Robert McManus objected to Mrs Kennedy's public support for abortion rights and gay marriage.
She later accepted the Boston College School of Law's invitation to give the keynote address at commencement.