One of the world's biggest multinational trade agreements moved a step closer to becoming reality on Thursday.

But it will be some time yet before countries can reap the benefits of the Trans-Pacific Partnership (TPP) - as the mammoth deal is called - with no guarantee it will even be ratified and implemented.

The TPP was signed by its 12 member nations on Thursday in Auckland, New Zealand. It is a far-reaching agreement involving 12 countries making up 40 per cent of the world economy: Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, the United States and Vietnam.

Besides slashing an estimated 18,000 tariffs, the TPP will set common standards in areas ranging from workers' rights to intellectual property protection. It will now undergo a two-year ratification period. The agreement will enter into force once at least six original signatories, accounting for at least 85 per cent of economic activity across the TPP countries, have ratified it.

This will not be an issue in Singapore, which has always come down firmly on the side of freer trade.

But the agreement has been plagued by controversy elsewhere. Protesters turned out strongly in Auckland, where the deal was signed. The pact has also drawn flak in the US and Canada.

Those against the TPP have expressed concerns about the secrecy in which the negotiations were conducted and the threats it poses to some local sectors. They also argue that it will likely protect the rights of large investors and corporations.

Countries will have to work to convince domestic stakeholders of the benefits of the TPP.

It also remains unclear whether US lawmakers will ratify the accord, which has sparked dozens of protests across the US and is set to be a hot-button issue at the upcoming presidential election.

All of these factors mean there are still significant hurdles to get over on the road towards freer trade.