U.S. President Donald Trump is keeping new tariffs in place on Mexico, Canada and China to pressure them to block the flow of the deadly opioid fentanyl into the United States, top White House economic officials said Sunday.

"If fentanyl ends, I think these [tariffs] will come off,” Commerce Secretary Howard Lutnick told NBC’s “Meet the Press” show.

“But if fentanyl does not end, or he’s uncertain about it, he will stay this way until he is comfortable,” he said. “This is black and white. You got to save American lives.”

Trump last week issued a string of whip-sawing tariff decisions that plunged the three major U.S. stock market indexes and roiled relations with Canada and Mexico, which are long-time U.S. allies and its closest neighbors, as well as its two biggest trading partners.