Members will vote on the proposed arrangement during a meeting in Newry.
An alternative proposal to broaden the arrangement to include Fine Gael and Labour will be tabled by members who oppose the plan.
Senior SDLP MLA Claire Hanna has said she will back the alternative motion.
Ms Hanna, the party’s Brexit spokesperson, said that she had a problem with the “exclusivity” of the arrangement and added she would never be a Fianna Fáil MLA.
However, Mr Eastwood has maintained the proposal will not lead to a merger in which the SDLP name and identity disappear.
He said he is confident a majority will back his plan.
“The bottom line in this is the SDLP brand remains, our integrity remains, our independence remains,” he said.
“What we’re talking about is a partnership to work together to meet the big challenges of the day.
“Brexit has changed the world and if the SDLP are serious about being a player in the future, we have to change too.”