Canadian tariffs on about $20 billion worth of U.S. goods took effect Tuesday, the latest escalation in a mounting trade conflict.

The previously-announced levies ranging from 15% to 50% affect a variety of products from steel and appliances to dairy and electronics. Canadian Prime Minister Mark Carney had said the tariffs would come in retaliation for levies that President Trump imposed on a similar volume of goods from Canada.

The tariffs are the latest flare-up in a trade war between the North American neighbors that has spanned Trump's second term in office. Late last month, the two nations looked close to a deal that would avert the latest wave of tariffs, but negotiations broke down in the final hours before a U.S.-imposed deadline, with each government blaming the other for walking away from the table.

Trump has already announced the next round of U.S. retaliation, which would increase tariffs on Canadian metals and vehicles to 50%. Those tariffs aren't scheduled to take effect until Jan. 1, giving the two nations time to negotiate.

Trump could, however, take other retaliatory action before then. On Monday, he posted on Truth Social that the U.S. should ban the sale of jets made by Canadian firm Bombardier, saying that Canada treats U.S. banks and aerospace firms unfairly. The administration has yet not taken any action to make good on that threat.