The creation by 11 Pacific Rim countries of a massive free trade zone brings with it a new test: Can and will the framework become a future magnet for additional members and, eventually, the United States and China?
The odds appear against it for now as the world's two largest economies are locked in an ongoing tariff war.
But Japan has a crucial role to play as a stabilizing force that is tasked with enhancing the appeal of multiparty free trade agreements that U.S. President Donald Trump is not a big fan of, political and trade experts say.