The Shark Tank star and ardent Kamala Harris supporter said in a post on X that Trump’s plan showed a lack of business understanding. Especially if the tariff on John Deere were to be lower than any imposed on China, it would be disastrous for the company, Cuban added.

“Good way to destroy a legendary American company and increase costs to American buyers,” he wrote.

During a policy roundtable in Pennsylvania Monday, Trump attacked the tractor maker’s plans, announced in June, to move its production of skid steer loaders and compact track loaders from Iowa to a facility in Mexico. The company has already laid off hundreds of workers in Iowa.

The former president and Republican presidential nominee said he would hit John Deere and any other company that did the same with a mega tariff because the move is “hurting our farmers, it’s hurting our manufacturing.”

“They think they’re going to make product cheaper in Mexico and then sell it in for the same price as they did before, make a lot of money by getting rid of our labor and our jobs,” Trump said.

In response to a request for comment, a John Deere spokesperson referred Fortune to a website touting its commitment to U.S. manufacturing.

“Deere is constantly reviewing production efficiencies and product/component moves to optimize manufacturing floor space in the U.S. and to leverage the highly skilled production workforce in the U.S. to build our most innovative new machines like the 9RX tractor,” the spokesperson said in a statement.

In a reply to other users on X, Cuban wrote that while he didn’t encourage American manufacturers to move to Mexico, he said that doing so was within the rules of the USMCA trade agreement that Trump helped orchestrate while he was in office. Either way, he wrote, tariffs are not the solution.

“The evidence is firm, that across the board tariffs are inflationary,” Cuban wrote.

The billionaire Shark Tank star has previously attacked Trump’s business record and said that while he doesn’t hate the Republican presidential candidate, he just thinks “he was and would be a lousy president.”

Cuban has boosted Vice President Kamala Harris since she announced she was joining the race in July. He has often promoted Harris as the better candidate for U.S. business and has even offered himself up as a possible future SEC chairman.