President Donald Trump late Thursday threatened a 35% tariff on goods imported from Canada, a dramatic escalation in an on-again, off-again trade war with America’s northern neighbor and one of its most important trading partners.

MSNBC's Lawrence O'Donnell and Jen Psaki discuss the breaking news that Donald Trump is now threatening Canada with tariffs of 35% claiming the "flow of fentanyl" from America's northern neighbor as his reason.

President Trump on Thursday threatened to impose 35% tariffs on goods from Canada starting next month, hiking import duties on one of the U.S.'s largest trading partners.

In a letter released on his social media platform, Donald Trump told Canadian Prime Minister Mark Carney the new rate would go into effect on August 1 and would go up if Canada retaliated.

Multiple states bordering Canada could feel the greatest impact of a 35 percent tariff on Canadian products starting August 1.

Marco Rubio meets with Russian foreign minister amid tensions over Ukraine and Trump releases tariff letters to trading partners.

President Donald Trump threatened a 35% tariff on some Canadian goods and raised the prospect of increasing levies on most other countries, ramping up his trade rhetoric in comments that weighed on stocks and boosted the US dollar.

President Donald Trump published a letter to Prime Minister Mark Carney on Thursday, accusing Canada of having "financially retaliated" against the U.S.

The president said the blanket 35% would be on top of tariffs on certain sectors. That’s higher than the previous 25% rate.

Doubling down on his trade wars, President Trump is threatening to raise taxes on many goods from Canada and punish Brazil for prosecuting his friend.