President Donald Trump said in an Oval Office signing ceremony Monday evening that his administration will impose 25% tariffs on Mexico and Canada on February 1, an extraordinary change in North American trade policy that could raise prices for American consumers.

The focus on American prosperity and national security is the latest pivot by Canadian officials as the country tries to find its footing with the new Trump administration, and - more urgently - avert the threat of blanket 25% import tariffs imposed by the US, its largest trade partner and closest ally.