Talks to secure a Pacific-wide free trade deal by the end of the year remain on track, but the prime minister is warning contentious issues could still derail it.

In a statement, the Trans Pacific Partnership leaders say they have made significant progress in recent months, and have told officials to work on resolving all outstanding issues by Christmas.

John Key says it's crucial the momentum to complete the deal continues, following Tuesday's meeting at the APEC summit in Bali.

Photo: RNZ

Mr Key says the prize - better access to a trade bloc that holds 800 million people and accounts for a third of world trade - is worth it.

But he warns contentious issues remain, including better access for agricultural products, stricter copyright protections, and giving corporations more rights to sue governments.

Opponents say the same difficult issues that could doom the talks, like access for dairy products and the treatment of copyright protection, have not gone away.

They argue the TPP gives unprecedented power to corporations, and undermines consumer, labour and environmental interests.

A critic of the TPP, Auckland University's Jane Kelsey, says it seems less likely it will be signed by its deadline at the end of the year.