Chaired by Dr Robin Eames, the Archbishop of Amagh and Primate of Ireland, the commission ended the third of its meetings in a series of "challenging" workshops without completing its report.

Further work will be needed before the final draft is presented to Dr Williams this month. The report is expected to make a "profound and practical impact" on the future shape of the Anglican Communion, a spokesman said.

Disciplinary action, including possible suspension from some or all of the governing bodies of the Anglican Communion, is expected against the Episcopal Church of the United States of America (Ecusa). The Anglican Church in Canada also faces a warning.

The crisis erupted last year after Canon Gene Robinson was consecrated as the Bishop of New Hampshire in the US and after the decisions of the Diocese of New Hampshire, Canada and the General Convention of the US Church to proceed towards the authorisation of public rites of blessing of same-sex unions.

But the impossibility of reaching a conclusion that will satisfy all parties became clearer than ever yesterday.

Anglican Mainstream, the multinational conservative evangelical group founded to oppose the appointment of Dr Jeffrey John, now Dean of St Albans, as Bishop of Reading, demanded "restorative discipline" on Ecusa that would reduce it to observer status for two years. During that time it should rescind its actions or face outright expulsion.

In a statement signed by leading global evangelical bishops and theologians, including the Bishop of Lewes, the Rt Rev Wallace Benn, President of the Church of England Evangelical Council, the group insisted thatr Ecusa "must not be able to use the label Anglican in a way that identifies them as part of the Anglican Communion".

The evangelicals also insisted that Ecusa's relationship with Canterbury, if it is to continue at all, must be "qualitatively different" from Canterbury's relationship with what will become the continuing Communion. They would need to have a clearly "diminished" status, Anglican Mainstream said.

There are already indications that if the African and Asian bishops' demands for discipline against the US are not met, leading bishops will set up a rival Anglican Church with its titular headquarters in an ancient see such as Alexandria. The Primate of Nigeria, the Most Rev Peter Akinola, has previously said: "You do not need to go through Canterbury to get to Jesus."

In the open letter on its website yesterday, Anglican Mainstream said: "If this request (for discipline) is ignored, then plainly we have reached the end of the Anglican Communion in its present form."

Liberals in this country said that the Church of England would break into "civil war" if the American Church were disciplined for its consecration of the Anglican Communion's first active homosexual bishop. The Dean of Southwark, the Very Rev Colin Slee, told The Church of England Newspaper that there could be mass resignations among clergy sympathetic to Ecusa's action.

"There would be outrage," he said. "I think a lot of clergy would consider resigning. This would be interference with the proper processes of an independent province, forced on them by other provinces who have no jurisdiction there."

This week, a US delegation of bishops met Dr Williams in a further attempt to help to resolve the matter.

Under the likely penalty, the US Primate, the Most Rev Frank Griswold, who is preaching at St Paul's in London tomorrow, would be barred from attending future primates' meetings because he presided at Bishop Robinson's consecration.

END