WASHINGTON — President Trump railed on Friday against Canadian tariffs on American dairy products as he prepared to travel to Canada, where he is likely to be greeted with an icy welcome ahead of a financial summit meeting with longtime American allies.

“We’re going to deal with the very unfair trade practices,” Mr. Trump said on Friday, and threatened to terminate the North American Free Trade Agreement if he cannot strike deals with American allies, a promise he campaigned on as well.

The president also suggested that Russia be brought back into the multinational alliance after it was kicked out in 2014. Mr. Trump is traveling to Canada for a meeting with the Group of 7, or G-7, an alliance among the United States, Canada, Britain, France, Germany, Italy and Japan. The president has already angered longtime American allies over his trade policies.