However, it's grassroots Greens members who will decide whether or not to accept it and they will meet in a crunch online meeting on Saturday afternoon.

Until then, New Zealanders will wait to learn the terms of the agreement, which is being kept secret until the Greens vote.

Ms Ardern's Labour claimed a decisive victory at the October 17 election, winning the party's strongest result since 1938 and a majority in the next parliament.

Since then, Labour has held talks with the Greens, which also won an increased number of MPs, on continuing their alliance into a second term.

Ms Ardern has spearheaded the talks herself, alongside deputy leader Kelvin Davis and finance minister Grant Robertson as well as key staff.

Greens co-leaders James Shaw and Marama Davidson have sat on the other side of the table, joined by their own advisers, with an ever-changing array of biscuits in the middle of the table.

Discussions on the snacks shared by the MPs have taken the place of substantive commentary on the talks, as both sides have agreed not to speak about the contents.

A fortnight of back-and-forth concluded in an in-principle deal between the leaders on Thursday.

That was confirmed by advisors on Friday, and as per the Greens' party rules, it must now be ratified by grassroots delegates.

The Greens have organised an online meeting beginning 4pm NZDT on Saturday for its roughly 160 delegates to discuss the proposal, which has the potential to be rowdy and boisterous.

The deal is likely to include ministries for Mr Shaw, already climate change minister, and Ms Davidson, and a commitment to pursue shared policies.

Given Labour's election showing, it is highly unlikely Ms Ardern has offered the minor party any real power.

If the grassroots Greens vote down the government offer, Labour will be left to fill the executive from its 64-strong caucus - the largest Labour partyroom in its history.

Australian Associated Press