Fianna Fáil and the SDLP are set to announce a joint partnership this week which will see parties both sides of the border working together.
However, there will be no merger of the two parties announced by leaders Micheál Martin and Colum Eastwood at a public event in Belfast on Thursday.
The Fianna Fáil parliamentary party meeting tonight was told of the agreement. Sources said there was unanimous endorsement of the commitment.
However, senator Mark Daly and Galway West TD Eamon O'Cuiv were not present at the meeting. Both previously were disciplined by Mr Martin previously after launching an event claiming an SDLP councillor would run under a Fianna Fáil banner. The move was immediately shot down by Fianna Fáil HQ.
Under the plan, strategies will be shared between parties and both would support one another, explained a key party member.
Nonetheless, both parties will remain independent.
Furthermore, members from both groups will be allowed canvass and campaign for each other in elections.
The partnership will likely see both parties working closely together on Brexit, among areas.
When asked last year about both parties working together, Mr Martin said:
"I think in terms of political ideology and narrative, there are many similarities between us and the SDLP."