President Biden came down hard on Kellogg on Friday, having chimed in on an ongoining strike involving 1,400 employees at four company plants, The New York Times reports. The company said it had plans to permanently replace the striking workers, who “voted down a proposed contract this week,” writes the Times.

“I am deeply troubled by reports of Kellogg’s plans to permanently replace striking workers,” Biden wrote in a statement, explaining that replacing striking workers is “an existential attack on the union and its members’ jobs and livelihoods.” 

Furthermore, “such action undermines the critical role collective bargaining plays in providing workers a voice,” the president said.

The strike began on Oct. 5, and has focused mostly on Kellogg’s “two-tier compensation system, in which employees hired after 2015 typically receive lower wages and less generous benefits than veteran workers,” writes the Times. On Tuesday, the union representing the workers voted against a tentative deal the union and the company had reached last week; in response, Kellog said it would “hire permanent replacement employees in positions vacated by striking workers.”

“I have long opposed permanent striker replacements and I strongly support legislation that would ban that practice,” Biden said Friday. “I urge employers and unions to commit fully to the challenging task of working out their differences at the baragaining table in a manner that fairly advances both parties’ interests.”