NEW YORK >> McDonald’s is partnering with Greek yogurt maker Chobani for its parfaits and smoothies in Southern California as the fast-food chain tries to transform into a “modern, progressive burger company.”

A McDonald’s spokeswoman, Lisa McComb, says the partnership is limited to a regional test in Southern California.

“It’s very premature to determine if it may expand,” she wrote.

McComb did not provide any other details, and a Chobani representative was not immediately available for comment. The partnership was reported earlier Tuesday in the San Diego Union Tribune.

The test comes as McDonald’s Corp. fights to step up its image, as sales have slumped amid changing tastes and intensifying competition. CEO Steve Easterbrook, who took over last March, has said he wants to transform McDonald’s into a “modern, progressive burger company.” One of the biggest moves under Easterbrook was the introduction of an all-day breakfast menu in October, which generated positive headlines for the company.

Whether it leads to sustained sales growth remains to be seen. In January, McDonald’s said sales jumped 5.7 percent at established U.S. locations in the last three months of 2015, marking its best showing in four years. But the company did not disclose how much of the increase was driven by an uptick in customer visits, versus factors such as price hikes.