Washington (CNN) President Donald Trump on Thursday continued his attacks on billionaire Charles Koch, his latest broadside against the conservative donor who is vital to Republican candidates.

"Charles Koch of Koch Brothers, who claims to be giving away millions of dollars to politicians even though I know very few who have seen this (?), now makes the ridiculous statement that what President Trump is doing is unfair to 'foreign workers.' He is correct, AMERICA FIRST!" Trump tweeted.

Trump's public attacks against Koch and his brother David, who recently retired, highlight a growing divide between the populist base of the Republican Party represented by the President and the business-minded wing that for years has relied heavily on the Koch brothers' financial support and influence.

The President was apparently referring to remarks Charles Koch made over the weekend, which were reported by some news outlets as describing Trump's trade policies -- which the Koch brothers have opposed -- as "unfair" to other countries. Koch, however, was arguing that Chinese subsidies hurt Chinese workers, but do not hurt American consumers who purchase those goods at a lower cost. Koch's main point is his belief that Trump's tariffs have hurt Americans.

"We should just get rid of all barriers ... We should let all goods in. So, they subsidize it? Yeah, it's unfair, it's unfair to their people. If they're selling goods to us at a low cost, you go to Walmart, they're going to discount it — oh, we can't do that, that'd be unfair to us? It's ridiculous."

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