Warren Buffett rebuked building materials company USG, and in what may be an unprecedented move, he voted against its board of directors slate.
The billionaire investor explained it was due to the company's unwillingness to sit down and negotiate with Germany-based Gebr. Knauf KG over the company's takeover bid for USG. Knauf had offered to buy USG for $42 per share on March 15.
"We did not think the [USG's] directors were essentially doing their job. We said we intended to vote against [them]. … We did vote against them," the chairman and CEO said in a "Squawk Box" interview with CNBC's Becky Quick that aired Friday.
Buffett said he believes it's unprecedented that Berkshire had voted against a board of directors slate.
"It's true I can't think of a time — there may have been one that skips my mind — that we've voted against directors, but we did not think they responded properly in terms of not sitting down and at least talking to Knauf," he said.
The company seemed to relent to Buffett's concerns.
On Tuesday, USG announced that its board of directors authorized management to start negotiations with Gebr. Knauf KG "regarding a potential sale of the Company."
"I think they responded properly," Buffett said.
Berkshire Hathaway is USG's largest shareholder with a nearly 30 percent stake in the company.
Buffett spoke to CNBC on Thursday evening from Omaha, Nebraska, where tens of thousands of Berkshire shareholders will be gathering this weekend for Saturday's annual meeting.