As the Trans Pacific Partnership free trade deal that covers 12 Pacific rim countries including the United States and New Zealand deal gets signed it is expected to significantly boost trade. But for the pact to take force, each country must now ratify it through its domestic political process.

The agreement covers a region responsible for about one-third of all world trade, although noticeably missing from the agreement is China, which is forging ahead with its own trade deals. Proponents say the agreement will increase trade and make it more equitable by eliminating most tariffs and other barriers. But opponents say it will erode national sovereignty and hand too much power to US corporations. The countries who have signed the deal are Japan, Canada, Mexico, Australia, Malaysia, Singapore, Peru, Chile, Vietnam and Brunei.

Whether the politically divided US will agree to it remains an open question. Many people in New Zealand remain opposed to the deal, and hundreds protested outside the Auckland venue where it was being signed, blocking traffic on some streets, while others protested in the capital, Wellington.

In the US, the agreement has been at the center of President Barack Obama’s trade agenda, but while it is supported by business groups and many Republicans, Senate Majority Leader Mitch McConnell has not yet backed it and has suggested Congress shouldn’t vote to ratify it until after the November elections.