Berkshire Hathaway Inc. increased its stake in H.J. Heinz to about 52.5 percent as billionaire Warren Buffett exercised a warrant in the ketchup maker ahead of its planned merger with Kraft Foods Group Inc.

Buffett was able to add a 5.4 percent stake in Heinz for 1 cent a share under terms of the 2013 deal when Berkshire and 3G Capital took the food company private. He purchased 46.2 million shares for about $462,000, Pittsburgh-based Heinz said in a regulatory filing Thursday.

Berkshire previously controlled about half the common stock, and also has preferred stake of $8 billion that pays an annual dividend of $720 million.

While Buffett is on the board of Heinz, the company is managed by Jorge Paulo Lemann’s 3G, which has been slashing jobs. Omaha, Nebraska-based Berkshire and 3G have agreed to combine with Kraft, where Lemann’s company has said it plans more cost cuts.

“Efficiency is required over time in capitalism,” Buffett, 84, said at Berkshire’s annual meeting in May. “I really tip my hat to what the 3G people have done.”