McDonald’s has said an emergency airlift of French fries to Japan has eased the nationwide shortage that forced the chain to ration them at more than 3,000 restaurants across the country.

From 5 January, medium and large-sized fries will be back on the menu, almost three weeks after the fast-food giant restricted customers to small portions due to import delays.

Labour disputes on the US west coast are curbing exports of fries, leaving Japanese restaurants scrambling to secure fresh supplies.

The Japanese arm of McDonald’s said it got around the problem by airlifting in more fries.

“We will continue to monitor the situation carefully to do our best to ensure stable supply of potato products,” it said in a statement.

Earlier this month, the company said it had airlifted more than 1,000 tonnes of potatoes and shipped 1,600 tonnes by sea from the US east coast, but it warned that would not be enough to ensure a steady supply.

US dockworkers are reportedly on a go-slow and have not been providing full crews for months in a bid to gain bargaining leverage in labour negotiations with employers, hampering exports to Japan.