Southeast Asian fast-food chains are being hit by a shortage of French fries as supply-chain snarls slow shipments of frozen items from the U.S. and Europe.

Signs at some of Yum! Brands Inc.’s KFC outlets in Singapore informed customers that the company would replace side orders of fries with potato waffles due to a “global supply disruption.” McDonald’s Corp. stores in Malaysia and Indonesia halted sales of large-size portions of fries late last month for the same reason, according to company notices posted on Twitter.

“The pandemic-related disruptions continue to have a multi-prong effect on the global supply chain and distribution network,” Diana Hoo, marketing manager at KFC Singapore, said by email. The company has some stocks of fries at its outlets in Singapore, but they are limited, she said.

Global supply chains have come under pressure from the omicron virus variant in recent months due to increased customs checks at ports and labor shortages across the transport sector. McDonald’s was forced to ration French fries in Japan late last year after flooding at Canada’s Vancouver port and the coronavirus choked off supplies. Fast-food chains generally use shipped frozen fries, rather than sourcing potatoes and making them themselves.

KFC Singapore’s fries are imported from the U.S. and Europe, Hoo said. Labor shortages and lower crop yields in the Pacific Northwest—where the famous Idaho potatoes are grown—have been exacerbated by congestion at U.S. and Canadian ports on the west coast, she said.

Container goods entering Singapore’s ports are also facing longer-than-usual delays. An average of 17 container ships per day waited to berth at the world’s second-busiest port in January, up from 15 vessels in December, according to logistics intelligence firm project44.