One of President Donald Trump’s chief trade policy architects offered a sobering statistic on Monday to critics railing against the chief executive’s new proposed tariffs on steel and aluminum imports.

As recently as the year 2000, the U.S. was the world’s largest producer of aluminum. By 2014, buried under an avalanche of cheap imports, domestic manufacturers accounted for just 3.5 percent of the world’s production. According to the World Atlas, the United States ranked sixth in the world in 2014 in aluminum production, at 1.72 million tons.

Peter Navarro, director of trade and industrial policy at the White House, said on “The Laura Ingraham Show” that China now makes 55 percent of the world’s aluminum.

“We import over 90 percent of our aluminum needs,” he said. “That’s how desperate that industry is for survival. So let’s deal with aluminum and steel.”

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Navarro’s comments came on a day that Trump suggested on Twitter he would use the tariffs as leverage to negotiate changes to the North American Free Trade Agreement (NAFTA).

“Tariffs on Steel and Aluminum will only come off if new & fair NAFTA agreement is signed,” Trump tweeted. “Also, Canada must treat our farmers much better. Highly restrictive. Mexico must do much more on stopping drugs from pouring into the U.S. They have not done what needs to be done. Millions of people addicted and dying.”

Trump sparked a furor last week by announcing he intended to impose tariffs of 10 percent on imported aluminum and 25 percent on steel made abroad.

Critics — particularly in Trump’s Republican Party — pounced, arguing the imports on two key manufacturing ingredients would drive up the price of everything from cars to beer.

But Navarro, who led a months-long review of domestic manufacturing and its importance to national security, said losing a steel and aluminum manufacturing base would put America’s military might at the mercy of sometimes-hostile foreign powers.

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Navarro said America has lost six aluminum smelters since 2013 and has just five remaining; only two are running at full capacity. He added that only one facility makes the high-purity aluminum used in the defense industry.

On steel, Navarro said 10 major facilities have closed since 2000, and the industry has shed 75,000 jobs.

“These tariffs are necessary to defend our aluminum and steel industry,” he said.

Navarro dismissed arguments by conservative economists and Trump supporters Stephen Moore, Arthur Laffer and Larry Kudlow, who argued in a recent op-ed in The Hill newspaper that Trump’s proposed tariffs jeopardize five million manufacturing jobs that depend on steel and aluminum inputs.

The argument is “factually wrong, bad math” from a trio of economists who never supported Trump’s trade agenda, Navarro said.

The White House adviser pointed to the president’s decision earlier this year to slap tariffs on foreign-made solar cells.

“You know what we got out of that?” he asked. “We got a flood of new foreign investment. And remember, those tariffs were higher.”

Related: Trump’s Tariffs Said to ‘Fulfill His Campaign Promises’ to Put ‘America First’

Indeed, Chinese manufacturer JinkoSolar announced after the tariff decision that it would build an advanced solar manufacturing facility in the United States.

However, in a reminder that trade is complicated, American solar company SunPower responded to the tariff decision by announcing it would lay off about 3 percent of its workforce in March.

But Navarro said he does not anticipate Trump buckling to pressure from corporate lobbyists or political opponents.

“I see none of that at all. He is resolute and courageous in the wake of all of this K Street, swamp uprising against what everybody should have expected him to do,” he said. “No, he has been firm about this. And he understands that if we don’t do this, we’re going to lose our steel and aluminum industries, and we won’t have a country.”

PoliZette senior writer Brendan Kirby can be reached at [email protected]. Follow him on Twitter.