A woman walks past an advertisement showing McDonald's burgers, fries and a drink, outside a McDonald's store in Tokyo December 16, 2014. REUTERS/Issei Kato McDonald's will cut down on portions of French fries from its menus in Japan, as the fast food restaurant faces a shortage of frozen potatoes, the Financial Times reports.

The website wrote that from Wednesday onwards McDonald's will only sell small portions of French fries. This is due to a shortage of imported potatoes caused by labour dispute at a port on the US West Coast.

Last week, more than 10 cargo ships were anchored at the twin ports of Los Angeles and Long Beach causing delivery delays for goods ranging from rice and frozen potatoes to NBA booblehead collectibles.

The crisis is partly the result of prolonged negotiations between the Pacific Maritime Association, which manages 29 American ports, and 20,000 dockworkers who have been without contract from June.

Japan is the biggest Asian market for American French fries, importing $336 million in frozen potato products last year.

The Financial Times reports that McDonald's, which has taken steps to fly in 1,000 tonnes of frozen potatoes to face the situation, still does not know how long the crisis will affect its Asian restaurants. More supplies shipped on a different route are expected between January and February.

The news adds to a string of troubles for the global brand. Facing declines in sales and traffic, the company is desperate to change its image among youngsters.

On Dec. 8, McDonald's reported a 2.2% loss in global same-store sales from the previous month.