A trade policy expert says there are several options for the future of the Trans-Pacific Partnership.

Our Government's ratified the trade deal, despite the US rejecting it.

Prime Minister Bill English is expected to flesh out the details with his Japanese counterpart next week on a visit to Japan.

Trade policy expert Charles Finny told Andrew Dickens the remaining 11 countries may just proceed with the TPP as it is without the States.

"Maybe there will be slight changes made to the agreement. Maybe it will be called something else, and maybe they will outreach to other countries.

"I think the sessions the Prime Minster will be having in Japan next week are very important because Japan and New Zealand are leading this process."

Mr Finny said there's a reasonably good chance one of those options will be decided on by the end of the year.

The Government formally ratified the trade deal yesterday and there's a meeting coming up in Vietnam at the end of the month.

The ratification of the trade deal is one of the first official movements on the deal since Donald Trump pulled the United States' support.

Mr English said there is still core interest in the TPPA  and in ratifying it, his Government's making that clear to the countries still involved.

He said Japan's ratified at their end as well.

"I'll be putting New Zealand's case for advancing without the US. I think we'd all like to think that in the long run, the US would become part of it," Mr English said. 

LISTEN ABOVE AS TRADE POLICY EXPERT CHARLES FINNY SPEAKS TO ANDREW DICKENS ON EARLY EDITION