The main owner of chocolate maker Hershey has rejected a preliminary takeover offer from Mondelez International Inc., people familiar with the matter said.

Mondelez International’s latest overture to Hershey underscores the challenges posed by high cocoa prices and penny-pinching consumers, which could make the company more open to a deal.

Mondelez International approved a stock repurchase authorization of as much as $9 billion, days after a report that the company was exploring an acquisition of chocolate maker Hershey.

Snack-food giant Mondelez International’s potential takeover of chocolate maker Hershey Co. would rank as the year’s top M&A deal.