The Minister said the government was fighting TPPA opponents with one hand tied behind its back, as it simply could not provide the real facts and figures while the discussions were still happening.
"We can't state what we know in precise terms to prove our case. But I wouldn't be making statements, and the Prime Minister wouldn't be making statements, along the lines that any increase in our health costs are going to be absolutely manageable, unless we were confident that we could back this up politically when the facts do come out," he said.
"We wouldn't be that dumb actually, politically, to start making these statements when we would be in danger of not winning the political argument later on."
Mr Groser admitted opponents of the deal were probably winning the political battle at the moment, but said they would not win the war.
"Once I've got a deal to recommend to the Cabinet, and for the Cabinet to then recommend to the New Zealand people through Parliament, I am extremely confident we will win the war. But at the moment all the noise is on the other side."
Agricultural trade special envoy at the talks, Mike Petersen, claimed New Zealand was not backing down - and said they were not going to be kicked out of the talks either.
"New Zealand and Australia and America are all fighting pretty hard to get better market access for dairy, particularly in to the large consumer markets, and we just need to see more progress in that area if we're going to get an agreement that we can all buy into," Mr Petersen said.
Mr Petersen believed there had been too much time and capital investment put into the deal for it to fail, and he was confident there would be a great outcome for New Zealand.
The secrecy cloaking the negotiations has been heavily criticised in New Zealand.
Prominent critic of the deal Professor Jane Kelsey, alongside Consumer NZ, the Association of Salaried Medical Specialists, Greenpeace, and Oxfam are about to go to the High Court seeking details about what has been discussed.
Professor Kelsey was hoping that would help shed some daylight on the process.
"Certainly this outcome makes it more possible for us to argue for the release of further documents before the negotiations are concluded."
Professor Kelsey said either way, more information was needed - and it needed to be clear, the level of secrecy around the negotiations, doesn't set a precedent for the future.
Professor Kelsey said she believed the price of the agreement will be high, whether it was in the cost of medicines for taxpayers or the inability to restrict foreign investment in residential markets.
"All of those are costs," she said. "At present there are no obvious benefits on the table."
"They should cut their losses, walk away, and find something more constructive to spend our taxpayers money negotiating."
Professor Kelsey argued everyone was blaming each other in Maui, but the underlying reason for the gridlock was the domestic opposition in almost all the TPPA countries.
Green Party trade spokesman Russel Norman is equally critical of the deal and its secrecy, saying the government should reveal what potential consequences would be for Pharmac, the ICT and dairy sectors, and for investor-state dispute settlements.
"The reason they don't want to tell us is because it will be very unpopular if people found out what John Key and Tim Groser are up to," Mr Norman said.
"If think this is such a great deal then why won't they tell us what's in it? Let's see what's in it so New Zealanders can judge."
Speaking to TVNZ's Q & A this morning, Mr Groser said he had "mixed" emotions about not reaching an agreement this week.
"On the one hand, of course I'm disappointed, but on the other hand, I'm relieved that we were able to avoid a situation of New Zealand essentially being thrown out of this negotiation or accepting a completely suboptimal deal on our number one export.
So you can understand why I say I've got mixed emotions. "When it came to negotiations around dairy, Mr Groser admitted it would not have been realistic to believe New Zealand was going to get everything it wanted out of the agreement, as it was a negotiation.
"But nor is it realistic to expect New Zealand to accept a completely suboptimal deal. And I don't know whether people thought we were bluffing or not.
You never know until you get to the endgame. But of course, we were never bluffing. And we've got to sit there and fight for New Zealand.
"But let me just say this: on all the rest of the deal, of great interest to exporters, there is a great deal shaping up. So it's a very complicated equation for us."
With the US elections coming up next year, it was difficult to say whether it would be end game if a deal could not be reached, Mr Groser told the programme.
"Well, the only honest answer to that is 'who knows?' There is no formally agreed timetable. But I've been telling the Prime Minister in numerous conversations I've been having over the phone with him that there is a very strong shared informal understanding that this has got to be done in weeks, not in months.
"Whether we get it done in weeks, not months, remains to be seen."
