By exempting Mexico and Canada from new tariffs, President Donald Trump is hoping to incentivize those nations to strike a fair deal on the North American Free Trade Agreement, Commerce Secretary Wilbur Ross told CNBC on Thursday.

"There's no question that the action the president took today is a further motivation to both Canada and Mexico to make a fair arrangement with the United States," he said in an interview with "Closing Bell."

"This is not being done, though, just as a negotiating ploy," he added.

Trump has repeatedly threatened to pull out of NAFTA if the nations can't find a way to overhaul the pact.

On Thursday afternoon, the president signed off on tariffs that slap a 25 percent levy on steel imports and a 10 percent charge on aluminum. Canada and Mexico are exempt from the tariffs, which will take effect in 15 days. The U.S. will also give other nations the opportunity to justify why they shouldn't be included.

"We are deadly serious about solving the problem in steel, aluminum and, as the weeks and months go by, other industries," Ross said.

He also reiterated his contention that the tariffs will not have harmful economic consequences.

Last week, Ross told CNBC the tariffs are "no big deal" and held up a can of soup to make his point that they will have a "trivial" impact on prices.

On Thursday, he said he used that soup prop to illustrate that the impact is "a fraction of a penny per can."

"Please spare me the idea that this is going to be massively destructive to our economy," he said. "All this talk about destruction in the other industries is simply not going to happen."