The Greens have backed Labour's flagship emissions trading scheme but New Zealand First says it will not make a decision until tomorrow.
Both parties discussed the scheme when they met at their regular caucus meetings today.
The trading scheme - the biggest part of Labour's plan to combatclimate change - has been the subject of intense negotiation between Labour, the Greens and NZ First for months.
The Greens had been wrestling with the decision about whether to vote for a scheme that the party still harbours serious misgivings about - but one that is probably more to its liking than what National would draw up post-election if it wins power.
A spokeswoman yesterday said public opinions on the bill sent to the party had been split roughly 50/50, and would be summarised when co-leader Jeanette Fitzsimons addressed her caucus.
Time is running out to get the lengthy bill passed into law before the election but after previously being cautious about its chances, Labour is beginning to sound more confident of success.
Prime Minister Helen Clark said yesterday negotiations were ongoing and the legislation was "poised for passage" as soon as there was enough support for it.
During her usual rundown of the legislative agenda for this week's sitting of Parliament, the Prime Minister for the first time mentioned that if the numbers were secured for the emissions trading scheme then it too would be slotted into the programme.
"I don't really want to comment at all on what would come to Parliament in the form of a Government SOP [amendment] if and when the bill arrives," she said. "We're continuing to work with both parties."
Helen Clark said she was "not necessarily" expecting a final decision from the Greens and New Zealand First today.
Asked how much longer Labour could wait for an answer, she replied "how long is a piece of string? That would give you a clue to when the election was".
