THE FREEST TRADER EVER:

The Trans-Pacific Partnership (TPP) will cover 40% of global trade

It is poised to be the world's biggest ever free trade deal and possibly its most ambitious. A dozen countries are negotiating the Trans-Pacific Partnership (TPP), which if successful, will account for two-fifths of world trade.

Those countries are the US, Japan, Brunei, Malaysia, Vietnam, Singapore, Australia, New Zealand, Canada, Mexico, Chile and Peru.

But will pushing through such a pact prove too gargantuan a task? And will China continue to be left out of talks?

Four experts give their views on what's at stake for the US, Japan, China and Vietnam.

Follow @brothersjudd