(Reuters) -U.S. dockworkers ratified a six-year contract that improved pay and benefits for 22,000 employees at 29 ports stretching from California to Washington State, the International Longshore and Warehouse Union (ILWU) said on Thursday.

Members of the ILWU voted 75% in favor of approving the West Coast port worker agreement that will expire on July 1, 2028. The deal, which is retroactive to July 1, 2022, includes a 32% pay increase over the span of the contract as well as a one-time bonus for working through the early days of the COVID pandemic.

Longshore workers covered by the agreement are based at some of the nation's busiest seaports, including Los Angeles/Long Beach - the busiest ocean trade gateway in the United States.

"The negotiations for this contract were protracted and challenging," ILWU International President Willie Adams said in a statement.

The union and the Pacific Maritime Association (PMA) employer group reached a tentative contract deal in June. That ended 13 months of talks and eased worries that related West Coast port disruptions could hit the all-important retail holiday shipping season.

West Coast ports lost some business to U.S. rivals on the East Coast and Gulf of Mexico as extended talks fueled uncertainty. The new contract provides a framework "to overcome new competitive challenges," PMA CEO Jim McKenna said.

(Reporting by Pratyush Thakur in Bengaluru and Lisa Baertlein in Los Angeles; Editing by Krishna Chandra Eluri and Sandra Maler)