A damaging split is threatening a crucial meeting this week called by the Archbishop of Canterbury in a bid to find a way forward for the troubled Anglican Communion.

Some archbishops from the conservative churches of the Global South are threatening to walk out of the meeting if liberal bishops, such as from the US, fail to pledge that their bishops will abandon support for gay marriage.

The rare primates' meeting, a gathering of archbishops and bishops who head the 38 worldwide Anglican provinces, was called last year by the Archbishop of Canterbury Justin Welby in an attempt to stave off a permanent split over gay clergy, bishops and gay marriage. One possible way forward would be a federal model similar to that used by the Lutheran churches of Scandinavia.

Insiders told the Mail on Sunday that between eight and 12 conservative archbishops from Africa and Asia will walk out unless the Episcopal Church leadership formally "repents", or the Archbishop of Canterbury asks the liberals to go first. The Episcopal Church angered the Global South by consecrating an openly gay bishop, Gene Robinson, in 2003.

It is understood that the three senior archbishops, from Nigeria, Kenya and Uganda, wanted to boycott the meeting in Canterbury but were persuaded to turn up and try to bring Archbishop Welby round to their side.

Lambeth Palace said: "The Archbishop has invited everyone. If people walk out that will be viewed with disappointment rather than anger, and the door will always be open."

One leading supporter of the conservative provinces, the retired Archbishop of Sydney Peter Jensen, writing for Anglican Ink, said: "The Christian faith is struggling to maintain its identity in the face of the secular challenge. Everywhere there is the sad tale of compromise and cultural enslavement. Everywhere we see the danger of Christians committed to a gospel without salvation, reconciliation without repentance, a Saviour without a cross and a Lord without a word."

He said the existence of GAFCON, the Global Anglican Futures Conference set up in response to the divisions, means that biblical Anglicans do not need to stand alone

"Truth matters even more than institutional unity. But true unity supports and nourishes the truth. The Evil One rejoices at the division of Christians. Far from being divisive, GAFCON is a great force for unity – it has saved and united Anglicans in the West and encouraged Anglicans in the South to realise that 'we are not alone'. But it has done more than that, for it is a model too for other denominations and churches around the world and encouragement for them to take their stand on the word of God."