The Vatican says Pope Francis has defrocked former US cardinal Theodore McCarrick after Vatican officials found him guilty of soliciting for sex while hearing Confession.

Defrocking means McCarrick, 88, who now lives in a friary in Kansas after he lost his title of cardinal last year, won't be allowed to celebrate Mass or other sacraments.

The punishment announced on Saturday for the once-powerful prelate and Archbishop of Washington comes a few days before Pope Francis is to lead an extraordinary gathering of bishops from around the world over the sex abuse crisis which has eroded the faith of many Catholics and threatened his papacy.

The US archbishop helping to organise next week's summit said on Thursday he expects to make 'significant progress' in responding to the scandal that's riven the church, and that lay Catholics will help to hold the hierarchy accountable.

Chicago Cardinal Blase Cupich told The Associated Press in a phone interview that the February 21-24 prevention summit is necessary for all global Catholic church leaders to understand they must act and be accountable to the victims for the abuse cases stretching back decades. He spoke of the urgency while acknowledging that victims and their advocates consider such a gathering long overdue.

'I think there is understandable frustration on that level,' said Cupich, hand-picked by Francis to help organise the summit. 'All I can say now is I believe we're going to make significant progress here. And we should also realise that we always have to keep learning — we can't get to a place that we think we have this nailed down. If we do that we're going to get it wrong.”