Winston Peters has finished a final meeting with Labour this evening, saying: "We should be finished by tomorrow night, but we're dependent on other people as well."
He said it was "doubtful" that he would know which direction the party favoured by the end of tomorrow.
"But what we'll be able to do is, now, as a caucus, sit down and say, 'This is what we can present to the party, this is what it looks like, and this is how quickly we can assemble that information'."
The New Zealand First board would meet on Friday, but Peters would not say where the meeting would take place.
Tomorrow his schedule begins with a NZ First caucus meeting at 8am, followed by a meeting at 9:30am with National.
Portfolios had still not been discussed, Peters said. "Sometime soon, but not now."
Earlier, Peters said there would have to be "serious consensus" with the New Zealand First board before the party decides whether to go with National or with the Labour and Green parties.
Negotiation meetings will wrap up tomorrow night, and Peters said the meetings tomorrow will be the "most substantive" so far.
"I can't answer the questions about what happens after that, because these talks may well determine that."
When the talks have finished, the New Zealand First board will weigh up the two options, he said.
"We will go to the board with both options ... You don't want to be going to a vote in these matters. You want a serious consensus. If you don't have a serious consensus, stay there until you get one. But who wants a 50/50 vote?"
Asked about what would be a consensus, he said: "We'd expect to have far higher than [75 per cent]."
"You'd need to assuage the concerns of anybody concerned about which way you're going to go."
A consensus would mean that everybody on the board would then be responsible for the decision, he said.
"Contrary to what you've been saying about Winston Peters making the decision, which is an outrage, actually ... but I've never it done that way."
He said an announcement on the next Government would be made "as fast as we possibly can".