(CNN) President Donald Trump's pitch on trade at the G7 in Canada will be no doubt a tough sell, especially since many prominent lawmakers -- from the President's own party -- are criticizing the idea of imposing tariffs on steel and aluminum imports.

"We've stopped the regulatory burden, we've made America's tax system more competitive, that produced certainty and great optimism in the economy, which is one of the reasons we've had these economic results," said Sen. Ron Johnson, a Wisconsin Republican. "Let's face it, we're now on the opening shots of a trading war, (creating) greater uncertainty and puts all that at risk."

A cadre of Republicans went to the White House on Wednesday to meet with the President on trade ahead of the G7 summit. Many of them concerned that taking a tough line on trade could ultimately back fire.

"We have the best economy we've had in decades and decades," said Sen. James Lankford, a Republican from Oklahoma. "I'd like to be able to keep that going, I don't want to have something be able to interrupt that."

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