Evangelicals have unveiled an 11th-hour bid to halt a move towards greater acceptance of the ordination of gay ministers in civil partnerships on the eve of the annual gathering in Edinburgh, which starts today.
An Edinburgh minister will call on around 730 clergy and elders to back the view that "marriage between one man and one woman is the only right and proper context for sexual relations".
The traditionalist push is likely to fail but could lead to a small number of ministers quitting.
Since the Kirk's struggle with the issue of gay clergy came to a head with the appointment of the openly gay Scott Rennie to an Aberdeen church in 2009, 13 ministers have left the Church, hitting 1% of the Kirk's 1389 congregations.
So-called liberal evangelicals have formed a network within the Kirk to push for a more traditional stance and their voice is expected to be heard in Wednesday's debate.
Under a counter-proposal from Rev Jeremy Middleton of Davidson's Mains Church in Edinburgh, gay ministers who remain celibate would be allowed.
Rev Middleton calls on the Kirk to: "Reaffirm the duty of the Church to minister to all people, regardless of their sexual orientation, recognising in particular the burden felt by those who struggle with same-sex attraction while striving to maintain a celibate life.
"Recognise that same-sex attraction is not, in itself, a barrier to leadership in the Church, including, without limitation, the ministry of Word and Sacrament, the diaconate and the eldership."
Two debates will take place on the same day, with the Legal Questions Committee hearing the hardline challenge and the Theological Forum suggesting backing the existing compromise, which allows congregations and Kirk Sessions to appoint a gay minister if they choose.
The forum said the current stance "offers greater transparency and legal security than an uncomfortable 'don't ask, don't tell' policy".
One evangelical alliance, Forward Together, welcomed the challenge while liberal group Affirmation Scotland said the move was disappointing.
Rev Peter Johnstone, of Ferryhill Parish Church in Aberdeen, who describes his position as progressive and is a member of Affirmation Scotland, said: "There is disappointment that this has been brought up."
He said that was the proposal presented last year by the conservative wing, with which the assembly had found compromise.
Forward Together said it "warmly commends this clear and concise statement of the Biblical position in relation to human sexuality and urges all commissioners to support it".
Ministers should "not act hastily" if it fails but regroup and "forward proposals for a united evangelical response", the group said.
The issue is likely to run into next year, with a call also from evangelicals to allow a vote on the result to go to presbyteries, and the same already planned if the status quo remains intact.
A spokeswoman for the Church said: "The Church confirms that Mr Middleton's counter-motion will be taken during the Legal Questions Committee debate on Wednesday. It is not appropriate to speculate at this stage on the outcome of that debate."