Jacinda Ardern has indicated it would be difficult to form a Government unless Labour or the Green Party gains more seats after special votes are counted.
The Labour leader has spoken to Winston Peters and said he was in "good spirits".
Efforts to form the next Government are gathering pace, with both Ardern and Bill English speaking to Peters, and the NZ First caucus meeting this morning.
Ardern expected special votes to favour Labour and the Greens, but told Radio NZ today that if that wasn't the case it would make forming a Government difficult.
"Certainly I think we would want to be in a more comfortable position. [The current vote] is enough to undertake those negotiations, absolutely.
"You would want a more comfortable majority... but I won't preclude ourselves from those negotiations regardless."
In preliminary results National won 58 seats, Labour and the Greens won 52 combined, and New Zealand First won 9.
In a 120 seat Parliament in which 61 is required for a majority, Labour and the Greens and New Zealand First have only 61.
The special votes - some 15 per cent of the total - usually favour the Greens and Labour. They will be released this Saturday.
Peters' MPs will meet in Wellington this morning and are expected to sort out the negotiating team.
English was first to make personal contact with Peters, calling him on Sunday and getting a call back yesterday morning. Although English was first to make contact, Jacinda Ardern called Peters soon after he spoke to English.
Peters may wait until Thursday to meet with Ardern and English as he has a funeral to attend on Wednesday.
The NZ First negotiations will be more complicated, given Peters can choose between the two and his options range from a full coalition inside Cabinet, a support agreement offering confidence and supply in return for some ministerial posts outside Cabinet, to sitting on the cross benches offering support on a case-by-case basis in return for minimal policy gains.
Both Labour and National are likely to push for a greater commitment than the cross benches to ensure stability.
Yesterday Bill English played down the impact the special votes could have, saying even if Labour and the Greens gained some seats the basic permutations remained the same.
"Even if National dropped back a bit we still have significantly more seats... and the combinations remain the same," English said.
"This would essentially be a new government designed to last for a number of terms and you want to get the basis for that clear at the start."
Ardern said she expected the special votes would boost the seats held by Labour and the Greens.
Asked if 61 seats would be enough to be in Government, Ardern said she was "seeking additional comfort beyond that range".
"But 61 still enables us to have those talks. To still be in the frame."
"Those [special] votes matter...but we are on a relatively tight timeframe. I think everyone's expectation is we move as quickly as we can."
Ardern rejected leaving the Green Party on the crossbenches as part of negotiations to form a government.
Asked whether she would entertain a hypothetical request for the Greens to be locked out of government position, Ardern today told Newshub's The AM Show she opposed the idea.
"I have had it suggested to me that they could simply sit on the crossbenches because they're easier to deal with. I've said I don't think that is a fair way to treat their support," she said.
But she would not confirm whether that meant she excepted Green MPs to have ministerial positions in Cabinet, outside Cabinet or just a confidence-and-supply agreement.
The Green Party campaigned on a change of government, and while not completely ruling out a deal with National, leader James Shaw has described one as highly unlikely.
"Just because the Greens have indicated where their support will go, does not mean we should disrespect the vote and support they bring," Ardern said.
She also played down the release of a January interview with Newshub in which Peters said free-to-air sport was a "non-negotiable" for his support.
"It wasn"t something that came up in the election proper," she said.