"At 10pm, roughly, the ministerial meeting finished. The view of the ministers in the room was that we had an agreement that was acceptable to all parties, and there was celebratory clapping and back-slapping.
"It was then turned over by ministers to officials to go through some of the completions to the changes to the text that had been agreed - and one of the parties said they had not reached agreement and that we don't have an agreement."
Parker would not name the country, but said it was not Canada.
Officials were trying to resolve the issue, Parker said.
"The deputy chair that was leading the negotiations yesterday was from Japan, and we understand it's been bumped up to the Japanese leader to deal with other leaders."
New Zealand is trying to opt out of the Investor State Dispute Settlement provisions, and Parker said that had been improved but not completely resolved.
He did not want to elaborate on what the sticking issue that reversed the done deal was, as it could prejudice ongoing negotiations.
Parker said it was unclear if the issue would be resolved tonight, but he said New Zealand was not blocking the consensus.
In the agreement he thought was reached, Parker said New Zealand got "some of what we wanted, but not all of what we wanted" in relation to the dispute clauses.
Parker said the issue holding up was clear, but he would not divulge it.
"It's rather unusual. The room thought there had been an agreement. When the ministers left, it became apparent that one party didn't think that was the case."
He said if there was a misunderstanding between ministers and officials, it was not on New Zealand's part.
"We work very closely with officials, and there's not a tissue paper between officials and ministers on our side."
Parker said the issue may have been over something that was lost in translation.
"It could be."
He said the issue was a serious one for New Zealand, though he was happy with the way he thought it had been resolved.
"It was an issue of contention for many parties in the room."
There had been confusion over the state of the deal.
Japanese Economy Minister Toshimitsu Motegi was reported yesterday as saying that ministers from the 11 TPP countries "agree in principle" on the trade pact, but did not elaborate. Mexican Economy Minister Ildefonso Guajardo also said that the countries had reached a deal, though he gave no other details.
But Canada's Trade Minister Fancois-Philippe Champagne denied that and said reports of an "agreement in principle" are "absolutely not true".
Jacinda Ardern arrived in Vietnam last week and said talks are now "down to the wire".
National's trade spokesman Todd McClay said New Zealand should stand up to the one country that was holding out.
"It's not unusual for the odd country to have a bit of buyer's remorse at the very last moment. The TPP countries, particularly New Zealand, need to stand up to any last moment demands that's probably only good for that one country.
"TPP11 will deliver hugely for New Zealand - it sounds like a deal is there to be done, and for New Zealand exporters, it must be done this weekend or I think TPP's all over."