The ban on two Sinn Fein ministers attending cross-border ministerial meetings is to stay in force, David Trimble has confirmed.
The Stormont First Minister has informed Martin McGuinness and Bairbre de Brun will not be able to attend because of the IRA's refusal to begin handing over their weapons.
Mr Trimble is to appeal against a High Court decision which ruled his decision unlawful.
The refusal by the Ulster Unionist leader to lift his ban is bound to add to the difficulties facing Taoiseach Bertie Ahern and Prime Minister Tony Blair as they attempt to solve the peace process deadlock.
Mr Trimble is preparing for crucial meetings with his party officers in Belfast later today, and party executive tomorrow, to consider the current state of the peace process.
Efforts by London and Dublin to get a comprehensive agreement on the issues of IRA disarmament, British Army demilitarisation and nationalist support for new policing reforms have so far failed.
Hardliners in Mr Trimble's party are likely to press in the absence of progress on decommissioning for a tougher stance from the party leadership towards Sinn Fein.