While the passage of trade promotion authority in the US will be a major victory, difficult market access negotiations remain for trade negotiators from the Pacific Rim countries before a deal is finalised.

Canada, facing an election in October, is proving to be a key hurdle, as the Harper government holds out on opening up its dairy and other agriculture sectors to competition from Australia, New Zealand and the US.

Japan and the US, the two major bilateral participants in the multilateral accord, need to reach a compromise on opening their agriculture and automotive markets to each other. Mexico is also a snag.

Dominos

These key dominos must fall before middle powers like Australia can settle on granting intellectual property concessions to US pharmaceutical giants, technology firms and entertainment companies, or whether local farmers and cane growers will be able to sell more sugar in the US and other markets.

It's been slightly embarrassing for the US, the ostensible bastion of free markets and capitalism, to almost capitulate to unions and oppose a free-trade deal.

Obama should have more forcefully advocated for the benefits of trade to Democrats months ago, instead of relying on eleventh hour support from Republicans.

In theory, a final multilateral deal could be signed as early as mid July when a tentative meeting of trade ministers is slated for Hawaii. Given the domestic political sensitivities of free trade in each country, a period of months seems more probable.

From there, Obama is required to provide Congress 90 days notice that he will sign the TPP and give lawmakers a chance to review the details.

Trade negotiators will need to move swiftly from here to conclude a deal, before the politicking ramps up late this year ahead of the 2016 US elections. China will be watching with intent.