By Supriya Kurane
(Reuters) - Billionaire activist INVESTOR (INVEB.ES)William Ackman's hedge fund has built a stake worth about $5.5 billion in Cadbury chocolate and Oreo cookies maker Mondelez International Inc
Pershing Square Holdings Ltd
"We welcome Pershing Square as investors in our company," Mondelez spokeswoman Valerie Moens said. "We'll continue to focus on executing our strategy and on delivering value for all our shareholders."
The Wall Street Journal, which first reported that Ackman had built a stake in Mondelez, said the activist investor wanted the snack maker to grow revenue faster and cut costs significantly or sell itself to a rival.
The newly formed Kraft Heinz Co
Kraft Heinz spokesman Michael Mullen declined to comment. Reuters could not immediately reach PepsiCo for comment outside regular U.S. business hours.
In 2012, Mondelez spun off its grocery business into Kraft Foods Group, which merged with Ketchup maker H.J. Heinz Co earlier this year to form Kraft Heinz.
As one of the hedge fund industry's most successful activist investors, Ackman's picks are closely watched by the market and often a company's share price will climb as he begins pushing for improvements.
With Ackman's disclosure, Mondelez now has two of the best known activist investors as significant shareholders. Nelson Peltz's Trian Fund Management LP holds a 3 percent stake in Mondelez, according to Thomson Reuters data.
Peltz, who is on Mondelez's board, played a role in the breakup of Kraft into Kraft Foods Group and Mondelez. Peltz said in April that he was not pushing Mondelez to do a big deal and wanted the company to continue improving its profit margin, sales and market share.
Reuters could not immediately reach Trian for comment.
Mondelez has taken several measures to cut costs, including shutting factories and "zero-based budgeting," which requires managers to justify every expense in each new budgeting period.
Last week, the company reported a better-than-expected second-quarter profit, helped by lower costs, and raised its share buyback plan by $6 billion.
(Reporting by Supriya Kurane in Bengaluru; Editing by Anupama Dwivedi)