The association is suggesting a single unionist candidate
The Ulster Unionists and DUP should discuss running a single unionist candidate in South Belfast, local UUP constituency members have said.
In a letter to UUP leader Sir Reg Empey, the Ulster Unionist Association suggested the move was needed to retake the Westminster seat from the SDLP.
The move could potentially bring the Ulster Unionists into conflict with their Conservative electoral partners.
The Conservatives have already selected a candidate for South Belfast.
It is understood a recent meeting of the South Belfast Ulster Unionist Association concluded that unless a single unionist candidate runs for Westminster, it is likely the seat will be retained by the sitting MP, SDLP Deputy Leader Alasdair McDonnell.
At the 2005 Westminster election Mr McDonnell won the seat with 10,339 votes. Jimmy Spratt of the DUP was second with 9,104 votes and Michael McGimpsey of the UUP was third with 7,263 votes.
Three Ulster Unionists are believed to be interested in standing this time - Mr McGimpsey, the former Belfast Mayor Bob Stoker and the Village community worker Paula Bradshaw.
The DUP's Jeffrey Donaldson said his party would back a deal with the Ulster Unionists whereby only one unionist candidate contested South Belfast as well as Fermanagh/South Tyrone.
"We're saying to the Ulster Unionists, look despite the fact we're the largest unionist party in both of these constituencies we're prepared to reach an agreement with you, whereby you contest one seat, we will contest the other.
"A single unionist candidate has a much better chance of winning the seat back for unionism," he said.
"But at least engage with us is our message to Sir Reg. I hope he isn't shackled to this notion David Cameron has that we have to split the unionist vote in every constituency in Northern Ireland."
Any suggestion of a pact with the DUP could cause problems with the Conservatives who have pledged to fight every constituency in the UK, and have already selected their candidate, former BBC producer Peter McCann.
Mr McDonnell said he would not be drawn into speculation about who would, or would not, be running against him.
"This speculation is simply a distraction and a bout of political posturing by those within the Ulster Unionist Party who are bitterly opposed to the Party's alliance with the Conservatives," he added.
South Belfast Alliance assembly member, Anna Lo, said the call for a joint unionist candidate showed that the UUP/ Conservative link-up remained "mired in the old politics of sectarian headcounts."
She said: "Clearly the rhetoric of a new non-sectarian dawn with support for a shared future has been exposed as completely shallow.
"We are not surprised at the stance of the UUP. The Conservatives need to reflect on what they have shackled themselves to."