He is standing in for US President Barack Obama whose domestic crisis in passing the Federal Budget has kept him from Apec for a second year in a row.
Last year the timing of the election kept him from Apec in Vladivostock.
The stated aim of the 12 countries is to have the deal done by the end of this year.
The goal was set at a meeting of TPP countries a year ago on the sidelines of the East Asia Summit in Cambodia.
Today's meeting is expected to re-affirm that goal.
But talking to New Zealand reporters in Bali, Mr Key also indicated it would be better for the negotiation to miss the deadline if it meant getting a comprehensive deal.
"In the end you don't get two bites of the cherry,'' he said.
"If we accepted a low quality deal, sure it might make the process go a bit quicker but the long term results would be significantly diminished and no one is going to start this process up again.
"It's either get it right first time or live for a long time with a poor quality deal. I don't think we want to be in that position.''
He said it would have been useful to have had President Obama there.
"The sheer mana and respect of the US president is always going to be extremely beneficial.''
But the United States Trade Representative, Mike Froman, was in Bali, and the US Secretary of State John Kerry was here.
"I don't think the message will be changing out of the United States even if the messenger is different.''
Mr Key also told a summit of business leaders in Bali it was important they became champions for free trade.
"If you speak out in your countries about the benefits of free trade you provide a voice which hopefully sits alongside the political voice of the benefits of free trade.''
"Your support, your vocal support can make a huge difference to chaning public opinion. I think that's important - that's very important.''