The Chicago-based chain started testing the loyalty program, which lets subscribers earn points they can redeem on burgers and fries, late last year in a few markets.

The company plans to expand the program nationally in the United States through the second half of this year, Chief Executive Officer Chris Kempczinski said during a June 2 conference at investment firm Bernstein, according to a transcript.

"We've been really pleased with what we've seen in Phoenix and New England where we've tested it," he said, with the tests aimed at making sure the program worked without slowing down drive-through operations.

He said McDonald's expects to have rolled out the program in its six biggest markets - including the U.S., Canada and possibly Germany - by the end of 2022.

"Loyalty becomes the gateway to knowing your customer," he said, adding the U.S. market will let the company see how much the program can boost sales.

(Reporting by Hilary RussAdditional reporting by Anna Driver in New YorkEditing by Chris Reese)

By Hilary Russ