ACT leader David Seymour says talks with National are progressing well and they are getting close to having a draft agreement.
The groundwork's been laid for a deal between National, ACT and New Zealand First, but there's still some way to go as efforts to form a new government enter the fourth week.
Seymour said they were "going to have to work together, as per the results of the will of the people confirmed on Friday, for about three years, over a thousand days" and he expected that would be "a strong working relationship ... the exact form of that obviously has to be negotiated".
It was getting to the point where ACT and National could start to lay out a deal on paper, he said.
"It's getting very close to that ... we've had several weeks of really productive discussions."
National leader Christopher Luxon has met with New Zealand First leader Winston Peters and separately with Seymour, but a meeting between the leaders of those other two parties has not yet eventuated.
Seymour has texted and Peters has said he has a plan to meet. Establishing a working relationship will be another key piece of the puzzle.
Despite not yet having met with Peters, Seymour said he expected "a strong working relationship between three parties".
"We're going to have to work together, as per the results that the will of the people confirmed on Friday, for about three years - over a thousand days."
After the final results of the election were unveiled on Friday, National will need both ACT and New Zealand First to govern, though both parties have raised red flags over the affordability of National's tax package.
ACT's wish for a referendum on the Treaty of Waitangi will likely be another tricky issue during negotiations.
National's leader Christopher Luxon on Monday told Morning Report his party would "deliver and run a government for everybody", saying a referendum on the Treaty would be "divisive and unhelpful".
Asked about Luxon's remarks, Seymour said: "He's made a comment to that effect, but ultimately, he also hasn't ruled it out".
"I think what everybody knows is that there needs to be a serious discussion around the role of the Treaty and how we find common ground."
Seymour said the country was facing "much bigger challenges" than coalition arrangements, including its fiscal position, ensuring streets were safer and figuring out how to "draw towards a better, more widely-understood conception of our founding document that unites rather than divides people".
Seymour said the challenges ahead were not "internal to the government" but were external, and broader than just inflation and the state of the economy.
"What do you actually do to make sure that the streets are safer? And how do you draw towards a better, more widely understood conception of our founding document that unites rather than divides people?"
Winston Peters arrived in the capital on Monday afternoon for a meeting with his caucus, but refused to answer reporters' questions as he walked through Wellington Airport.
"Can you fix this up for us?" he quipped to some waiting taxi drivers, gesturing toward the press pack, before hopping in a cab and departing.
Labour is also likely to meet as a caucus tomorrow, where it is possible they will hold a vote to endorse Chris Hipkins as leader.