The Ulster Unionists and the Alliance Party have been in negotiation about a possible electoral pact to maximise the performance of pro-agreement candidates in the British general election.
The Irish Times has learned that the two party leaders, Mr David Trimble and Mr Sean Neeson, have discussed the issue, while two nominees from each side have explored the options in-depth in three or four meetings since February.
Unionist enthusiasts for a formal pact say it could prove crucial to the UUP's hopes of beating a strong challenge from the DUP's Mrs Iris Robinson in Strangford, and to Mr David Burnside's chances of reclaiming the South Antrim seat his party lost to the Rev William McCrea of the DUP in last September's by-election.
The Alliance Party has already boosted the prospects of the sitting pro-agreement Ulster Unionist MP, Mr Cecil Walker, by confirming it will not field a candidate in North Belfast, which Mr Nigel Dodds of the DUP appears confident of winning in the election.
It is understood the negotiations about a deal are currently stalled because of the reluctance of the UUP to allow Alliance a "free run" against the DUP deputy leader, Mr Peter Robinson, in East Belfast.
However, the Alliance leader, Mr Sean Neeson, last night insisted "the door remains open", and said Mr Tony Blair's delay in calling the election allowed time for the parties to recover the situation. Mr Neeson also disclosed that the SDLP had ignored similar overtures from his party.
The Alliance leader acknowledged that "the opportunity may be squandered" but said: "I believe politics is still the art of the possible. I'm prepared to talk to anybody about maximising the potential vote for pro-agreement candidates."
But he added: "I'm deeply disappointed that the Ulster Unionists simply wanted us to roll over [in East Belfast] and that the SDLP for their own reasons didn't want to know."
Other sources close to the talks suggested that in addition to possibly strengthening the UUP's position in Strangford and South Antrim, a pact could mean a significant boost to the party's hopes of winning North Down from the sitting UK Unionist Party MP, Mr Robert McCartney.
Mr Trimble's supporters are engaged in an effort to de-select the prospective Ulster Unionist candidate in North Down, Mr Peter Weir, and to have him replaced with the pro-agreement Lady Sylvia Hermon.
However, Mr Trimble is under some internal party pressure to intensify talks with Alliance about a pact. "Every seat should be examined," said one senior unionist source last night. "Here's a real chance to beat the DUP. We should not allow personalities to get in the way. If the agreement collapses it will quite simply be as a result of lack of leadership and vision."
Supporters of a deal point to the results of the 1998 Assembly elections. In Strangford, anti-agreement unionists had a 3,146 first-preference margin over the UUP, while the Alliance claimed almost as many votes - 2,947.