Bill English told the AM Show today that negotiations have not been completed and there are still a lot of issues to be discussed.
He is to meet the NZ First board today, the show reported.
English also told the AM Show that letters had been exchanged over the weekend but he did not have a deal to take to National's board.
"It's quite important people understand the discussion NZ First are having today is another step in the process but it's by no means the final step in actually agreeing a government," English told the show.
Ministerial positions had not been discussed, English confirmed.
Earlier, Peters told Newstalk ZB that the process had been far more complex than he had originally thought it would be.
Peters said he worked over the weekend ahead of the caucus and board meeting in Wellington today to firm up the precise agreements with National and Labour, and contact with them had been "reasonably extensive".
But there had been no discussion on ministerial positions and he made it clear he wants the decision to be made without reference to them.
"The danger of these sorts of talks is when people get ahead of themselves and concern themselves with positions and preferment and things like that and policy gets sacrificed on the way through.
"The last thing we want is for that to happen. That's the fact. We have not talked about it to anybody."
The meeting, nine members of the caucus and 12 members of the board, would have an enormous amount of information to sort through, Peters said.
"If we need any further information we have the capacity to quickly call up and sort it out."
Peters said the decision was unique and complex in his political career.
"I've never had a decision to make like this in the context of the potential positive side of it.
"I've had to make decisions in my career which have been 'I'm not going to accept this and I'm going to have to leave and I'm going to have to make a stand here'."
But because of peculiar circumstance it was an extraordinarily awkward and complex situation, which he might be able to explain better in the future.
"It has been much more complex than I originally thought before the election and on election night," he said.