WASHINGTON, May 31 (Reuters) - Transportation Secretary Pete Buttigieg on Friday said major U.S. airlines had declined to commit to boosting travel benefits for military personnel, the latest clash between the Biden administration and the air carriers.

Buttigieg in April had urged airlines to do more for military personnel and vowed to publicize the issue on a dashboard but he said major carriers including Delta Air Lines , American Airlines and United Airlines have declined to "make clear and enforceable commitments to U.S. service members and their families."

Airlines, who employ a large number of military veterans, insist they go beyond what USDOT is measuring benefits but some say do not want to add those benefits to customer service plans, which would then open them to USDOT enforcement actions if they did not abide by those commitments.

Airlines for America, a trade group representing the largest U.S. passenger airlines, said the dashboard "shows only a fraction of what airlines offer service members" and said it "fails to reflect the numerous benefits carriers already offer."

The dashboard measures whether airlines will voluntarily commit to waiving cancellation and change fees and ensure full refunds for service members and family who cancel or reschedule travel plans due to military orders; offering some free baggage and the lowest fare for flights to visit service members recently injured in the line of duty.

"Service members and their families make extraordinary commitments and sacrifices for this country, and they deserve support and recognition whenever they fly," Buttigieg said.

Six of the 10 airlines received no green checkmarks from USDOT, including the largest three airlines along with Alaska Airlines, Hawaiian Airlines and JetBlue Airways .

Allegiant and Spirit Airlines got four checks and Frontier three.

Southwest Airlines received two checkmarks because of its existing baggage and change fee policies applying to all passengers.

Airlines and the Biden administration have repeatedly clashed on a number of customer service fronts.

Earlier this month,

major airlines sued USDOT

over a new rule requiring upfront disclosure of airline fees.

Airlines for America filed suit over USDOT rules last month requiring airlines and ticket agents to disclose service fees alongside the airfare, saying it would help consumers avoid unneeded or unexpected fees.

USDOT has created other dashboards since 2022 measuring other airline customer service benefits and was directed by Congress to create a new one on minimum airline seat size. (Reporting by David Shepardson Editing by Marguerita Choy)