While Burger King has been adding restaurants and growing comparable sales internationally, in the United States it has struggled with bankruptcies by two big franchisees.

In the first quarter, Burger King closed a net 124 U.S. locations or 1.7%, to end the quarter with just under 7,000 U.S. restaurants, according to its earnings release.

This year, the brand is seeking additional franchisees with stronger finances but still expects to close between 300 and 400 more restaurants, Chief Executive Joshua Kobza said during a call with investors. Usually, it closes a couple hundred annually, he said.

"There will always be a minority (of franchisees) who aren't dedicated, enthusiastic operators," Chairman Patrick Doyle said on the call.

"We'll work with them to leave the system," Doyle said.

The fast-food chain's $400 million turaround plan, dubbed "Reclaim the Flame," appears to be building market share, bringing new life to run-down restaurants, updating menus — and attracting younger customers.

Burger King's U.S. comparable sales rose 8.7% in the first quarter.