Bentonville, Ark. (CNN Business) Walmart CEO Doug McMillon thinks the federal minimum wage is "too low." Now the head of the country's largest private employer is calling on Congress to raise it beyond $7.25 an hour.

"The federal minimum wage is lagging behind," Doug McMillon said at Walmart's annual shareholder meeting in Bentonville, Arkansas on Wednesday.

, along with workers' rights groups, have called on Walmart to raise its wages above the company's current $11-an-hour minimum. Congress has not raised the minimum wage since 2009 , but McMillon's surprise comments may give lawmakers an incentive to act. McMillon's call may also ease pressure on Walmart. Senator and presidential candidate Bernie Sanders , along with workers' rights groups, have called on Walmart to raise its wages above the company's current $11-an-hour minimum.

McMillon said "it's time for Congress to put a thoughtful plan in place" to increase wages. It was the first time he has pushed Congress to raise pay nationwide, according to the company.

Any plan to increase the minimum wage, however, should take into account cost of living differences around the country "to avoid unintended consequences," McMillon said. He also noted that a hike may need to be phased in over time.