Mr Goff, who launched the TPP proposal when he was Trade Minister in the Labour Government, is facing resistance to the deal from unions affiliated to Labour, but the party has agreed to reserve its positionofficially.
The United States is leading the negotiations and President Barack Obama set the end of this year as an informal deadline by which to conclude the deal.
But few expect the deadline to be met.
Mr Goff said he thought it was more likely the deal would be concluded towards the end of March next year.
"I've never been in any trade negotiation yet that has beaten a deadline. More often they have missed a deadline and taken longer than they thought."
He said it was not a matter of American multinationals being able to get everything they wanted in talks, as much as they might imagine they could.
The US, including the Congress, had to accept there had to be significant compromise from all countries.
Mr Goff said opponents of the TPP were seeing the talks through their particular lens "and they are highlighting worst-case scenarios" and he was not criticising them.
"It's unlikely we will get to a worst- case scenario and if it was a worst- case scenario, it is unlikely that we would agree to it."
TPP in brief
• TPP Trade Ministers have just finished their first meeting in Singapore.
• Negotiations began in March 2010, after President Barack Obama endorsed George W. Bush's commitment to join.
• 12 countries are now negotiating: US, Canada, Mexico, Peru, Chile, Australia, New Zealand, Singapore, Malaysia, Brunei, Vietnam, Japan.
The deal covers more than just market access and tariffs.