"What always haunts a Prime Minister is 'will there be a series of trade blocs develop that you are not part of?' Because that is unthinkable for New Zealand as an export-oriented, small trading nation," Clark said.
"So of course New Zealand has to be in on the action with the TPP and go for the very best deal it can as the agreement expands beyond the original four economies to a wider regional agreement."
The Labour Party Clark once led has said it will not support the TPP unless "non-negotiable bottom lines" were met.
Those included gains for farmers, protecting Pharmac, ensuring Governments could not be sued for regulating in the public interest and maintaining the right to restrict farm and housing sales to foreigners.
Labour leader Andrew Little said Clark "has her views".
"I'm not quite sure what information she has got about the content of the negotiations.
"But I think the critical thing is, this agreement differs from any other agreement on the basis that if there is stuff in it we don't like, or in a few years' time we just find it is hugely problematic for us, our ability to negotiate our way out is virtually impossible."
Mr Little said it was hard to gauge whether TPP would get over the line, but a good deal for dairy was "absolutely crucial".
"If we don't have anything significant to show there, the question is, why would we be in it? Even if they do sign something off, we won't know for another month or two about what the content is. We just don't know."
Helen Kelly, president of the Council of Trade Unions (CTU), said she was not critical of Clark having an opinion on the TPP, but "I don't agree that you have to be in to win".
"That hasn't proved to be the case when countries have signed up to bad trade deals."
Ms Kelly said the TPP would trade off a range of sovereign powers which the last Labour Government used to improve New Zealand society.
"Things like re-nationalising rail, setting up Kiwi Bank, promoting New Zealand culture and music and defending state services like health, which Labour was really good and strong on. Some of those things would be in jeopardy if the agreement is signed."
On the current TPP negotiations, Mr Peters said he did not think the US, Canadian and Japanese farming interests would allow New Zealand a fair deal.
Mr Peters said the Korean FTA with New Zealand was a poor deal, and other countries had better deals with China than our FTA. Countries such as Norway and Switzerland showed being out of trade agreements was not fatal.
After meeting Clark earlier this week, Mr Key said her opinion on the TPP was correct.
"She started some of these discussions a very long time ago and we would hope the Labour Party would see that in New Zealand. This isn't about politics - it's about enriching New Zealand."
He said modelling had shown it would be more lucrative for New Zealand than the free trade agreement with China, even with a less than satisfactory deal on dairy.
He confirmed Trade Minister Tim Groser had now travelled from New York to Atlanta to attend the negotiations - something Mr Groser previously said he would not do if the parties were still so far apart a deal did not seem possible.
It was still possible the talks would conclude this week. If not, the last possible chance would be the Apec meeting in the Philippines later in the year.
