OMAHA, Neb. — Investor Warren Buffett’s company plans to vote against USG Corp.’s four board nominees in another signal that Berkshire Hathaway may support Knauf’s $5.9 billion bid to buy USG.

Buffett’s assistant Debbie Bosanek said Thursday that Berkshire will vote against the directors nominated by USG.

Berkshire owns 31 percent of USG’s stock and is the biggest shareholder in the Chicago construction materials company.

Last month, USG rejected Knauf’s bid for the company because it said the $42 a share it offered was inadequate.

But Berkshire said at the time it would be willing to sell its 43 million shares to Knauf at that price if the German company could reach a deal to buy the entire company.