US President Donald Trump promised to impose a wide range of tariffs soon after taking office, including on America's closest neighbors. His press secretary has confirmed that he is carrying through on that pledge.

At a news conference on Friday, Karoline Leavitt said: "The president will be implementing tomorrow 25 percent tariffs on Mexico, 25 percent tariffs on Canada, and a 10 percent tariff on China for the illegal fentanyl that they have sourced and allowed to distribute into our country, which has killed tens of millions of Americans. These are promises made and promises kept by the president."

Leavitt added that the tariffs will go into immediate effect on Saturday. She did not say whether any imports will be subject to exemptions.