The US-Mexico border is effectively closed off to migrants seeking asylum in the United States within hours of President Donald Trump taking office, an extraordinary departure from previous protocols that has left many concerned migrants in limbo.

President Trump is using the threat of stiff tariffs on goods from Canada and Mexico to pressure the two nations to start renegotiating a continental trade deal.

While much about the threatened tariffs is still unclear, experts predict they would be bad news for all three economies, with few winners.

Trump underscored his intention to use tariffs, a tax on foreign goods, as a tool of international economic policy and an increasingly vital source of government revenue.