Peters told Newstalk ZB he had not yet decided whether he would advise both English and Ardern of his decision before a public announcement.
Listen to Barry Soper's exclusive interview just after 7am here
It is understood the policy offers from the two parties are so finely balanced that the final decision could hinge on what English and Ardern have offered up since further talks with Peters over the past 24 hours - such as ministerial positions.
Those matters were dealt with by the leaders rather than negotiating teams.
In a statement, Peters said he spoke to both Ardern and English yesterday about the timing of an announcement "amongst other matters".
Those "other matters" are understood to include ministerial positions.
NZ First's list is likely to include Foreign Affairs and Economic Development - as well as what place NZ First would get in a Government.
The Herald understands NZ First's preference is for a full coalition agreement with ministerial positions inside Cabinet.
As crunch time looms, English has also summoned National's MPs for a caucus meeting this morning to update them on the talks, but stressed he had no indication of what the NZ First decision would be.
National's board would also have a teleconference after that. Both caucus and the board will have to sign off on any agreement.
The decision could also rest on who Peters is more comfortable working with - his reservations about English stem from a difficult history but there is also concern about whether Ardern has the experience to wrangle a three-party governing arrangement as Prime Minister.
Other NZ First caucus members had little to say as they left yesterday - deputy leader Ron Mark said "the boss" would make any statement and Shane Jones also referred everything to "the rangatira".
The Green Party is also yet to hold its special general meeting of 150 delegates to sign off on its agreement with Labour.
A time slot has been booked every evening over the past week but the Greens were waiting to be told when to go by Labour - and the meeting would likely not happen until NZ First had committed to a Labour-led Government.
National and Labour will also have to have any agreement signed off by their boards and caucus - but that process can be quick.
Peters' decision has taken longer than he initially anticipated when he said he expected a decision by October 12. The potential for a significant change in the results from the special votes meant he waited until those were in before starting negotiations in earnest - which gave only five days for those talks.
Peters defended going over that deadline, saying it was important to conduct the process properly and give both parties a fair go.
Peters also took exception to claims it was ridiculous that a party on 7 per cent was in the position of deciding the next Government.
"Seven per cent, or 10 per cent or 20 per cent or for that matter 45 per cent doesn't make the next Government. A majority of the votes in Parliament make that decision, and that's what the outcome will be. This is a majority decision of Parliament in the end, not a minority decision."
