Following his meeting with National this morning, New Zealand First leader Winston Peters said "huge progress" was being made, but he refused to go into detail about which policy areas were being discussed.
"We're making huge progress, finding out what we agree on, what we don't agree on, what we can still negotiate on, where we might take things into the future by cooperation.
"So at the end you may not have their decision or our decision as the policy, but a mutual decision."
New Zealand First and Labour wrapped up their first meeting of the day more quickly than expected. Mr Peters said the talks went very well and "faster than we thought".
The meeting ran for about an hour and three-quarters.
Mr Peters said there had still been no discussion about possible portfolio or ministerial positions for his MPs in any deal.
"It's all about policy... We've never mentioned anything about personal preferment or position at all."
Leaving the meeting, Labour leader Jacinda Ardern said they had made "excellent progress" working through policies important to both parties.
The New Zealand First team is expected to meet with both parties again later in the day.
Green Party leader James Shaw has said he trusts Labour's Jacinda Ardern to represent his party's interests fairly in talks with New Zealand First.
Talks towards forming a government continue at pace at Parliament today.
While New Zealand First leader Winston Peters said a decision on any deal would be made by tomorrow, he has not yet put a timetable on making that decision public.
Day four of talks and parallel negotiations between New Zealand First, National, and Labour, continue.
Labour has also been meeting daily with the Greens, who would be needed to make up the numbers in any deal with New Zealand First.
After meeting with Labour this morning, Green Party leader James Shaw said he trusted Labour, and its leader, to fairly represent his party's interests in the coalition talks.
"Jacinda made ... fairness one of her principle values in the campaign.
"I've known her for a number of years ... I trust her and she seems to be doing a good job of it."
He said any deal would have to deliver a "stable and responsible" government that would last.
"So presumably all of the partners have got to be pretty comfortable with its direction and that's the same as any other coalition government."
Mr Shaw would not comment when asked if sitting on the cross benches was an option for the Greens.
Once an agreement has been struck all parties would have to go through a ratification process.
The Greens have to hold a special meeting of national delegates, and that could be held online or via phone conference.
Labour's 20-member Executive Council would sign off on any deal.
And National and New Zealand First would consult their respective board and caucus.
Mr Peters would not say if his party's board would convene on Thursday night to talk over any decision.
Nor would he be drawn into whether an announcement would be made before the weekend.
New Zealand First's negotiating team met with National this morning, and will meet with Labour this afternoon, with two further meetings expected later in the day.