The president’s vision for reshaping global trade is falling into place, but he is embarking on an experiment that economists say could still produce damaging results.

A fresh trade deal between Washington and Tokyo, with Japan pledging investments in the US and opening up its long-protected agricultural sector in exchange for lower tariffs, underscores how even long-standing US allies are not shielded from President Donald Trump's "America first" push to reshape the global trade paradigm,