The United States is one of the dominant economic players in the world. Successive Administrations have campaigned vigorously for free trade.
Through the major international financial institutions the United States has a big say in setting the international trading rules which all countries have to follow.
But how far does the United States itself seek to evade these rules?
Jonathan Marcus travels to farms in Mexico and the American heartland to examine the impact of US trade policy.
He looks at who benefits from free trade. And he sets out to explore how far the process of globalisation is inextricably bound up with the promotion of US interests.
Read more on the growing global anger over US trade policies