TheTory Party is dismissing the chances of a South Belfast unionist unity pact as “zero” despite a controversial joint candidate move in Fermanagh and South Tyrone.
DUP leader Peter Robinson has pressed for agreement in South Belfast on the back of a deal in the west of the province.
And his party is expected to crank up the pressure on the issue in the days ahead.
But while the UUP's Tory allies have shifted position on Fermanagh, sources are firmly ruling out any further moves.
Asked yesterday for the odds on a unionist unity pact in South Belfast, a well-placed Tory source told the Belfast Telegraph: “I'll give it to you in percentage terms — zero. It's inconceivable.”
The Conservatives had vowed to contest all 18 Northern Ireland constituencies under their electoral pact with the UUP.
Instead, both parties and the DUP will now be supporting unionist unity candidate Rodney Connor in Fermanagh and South Tyrone.
Mr Connor, former chief executive of Fermanagh Council, has said he is prepared to accept the Conservative Party whip if elected.
However, he will stand as an independent and would sit in the Commons with that status.
Mr Connor also said that “on matters affecting Northern Ireland I shall vote on the basis of what I believe is in the best interests of the people of Fermanagh and South Tyrone”.
The Tory/UUP project came under fire from nationalist parties and Alliance in the wake of the candidate deal.
Defending the move, the Conservative's Shadow Secretary of State Owen Paterson said: “We recognise that Fermanagh and South Tyrone has characteristics that are unique within the UK.
“It has been without any democratic representation for the past nine years.
“It is the one constituency where there is currently an abstentionist MP, where a single cross-community candidate could lead to the restoration of democratic representation at Westminster.”
Mr Robinson welcomed the agreement on Mr Connor's candidacy, saying: “This should represent the beginning of greater co-operation within unionism and be a platform on which we can build for the future.
“Whilst South Belfast does not have an abstentionist Member of Parliament, there is also the opportunity there whereby a unionist MP could be returned if there was agreement within unionism on an independent candidate.
“The enthusiastic support coming from people in Fermanagh and South Tyrone at the news of Mr Connor's candidacy demonstrates just how important it is that we continue to seek the same kind of agreement in South Belfast.”
The two rival unionist candidates for South Belfast — DUP Assembly member Jimmy Spratt and Tory-UUP hopeful Paula Bradshaw — are already firmly on the campaign trail.
The SDLP’s Dr Alasdair McDonnell is bidding to retain the seat which he won in 2005 thanks to a split unionist vote.
He hit out at the DUP's push for a voting pact, saying: “They would rather have a Dr Who than a Dr McDonnell returned on May 6 next to represent the electorate in South Belfast.
“The sad reality is that the DUP strategists are still hell bent on trying to stop progress at the expense of keeping alive their time warp nightmare.”