First came a hitch to butter supplies just as millions of Japanese prepare to tuck into Christmas cake. Now the country’s fast food lovers are contending with a shortage of french fries due to a labour dispute taking place on the other side of the Pacific.

More than 3,000 McDonald's restaurants in Japan - the biggest Asian market for US frozen potato products - said on Tuesday they would sell only small-sized portions of fries for the foreseeable future amid severe delays in imports of thousands of tonnes of the chain's staple accompaniment to a Big Mac.

The long transit times, which have more than doubled to between two and four weeks, have been blamed on a protracted dispute between 20,000 dockworkers and terminal operators and shipping lines at 29 ports on the US west coast.

The supply line has been further disrupted by a shortage of equipment to handle cargo, as well as rail service delays and the introduction of super-sized cargo vessels, reports said.

In response McDonald’s Japan took the emergency step of importing 1,000 tonnes of frozen fries by air. They began arriving earlier this week but another 1,600 tonnes from ports on the US east coast won’t land until late January.

Management say they are bracing for a possible shortage during the normally busy holiday season, although they believe the portion restrictions will prevent them running out altogether.

"Unfortunately, without this sales restriction step, we would run the danger of running out of fries at some of our stores around the end of the year or beginning of the new year," McDonald's Japan spokeswoman Kokoro Toyama told Reuters.

There are no restrictions on the number of small portions customers may order but the company is unable to say when the medium and large portion sizes will reappear.

Guardian