Japan, Asia's second-biggest wheat importer, may increase prices for flour millers by the most since 2008 as weather problems from Australia to North America curb supply, said Nobuyuki Chino, president of Unipac Grain Ltd.

Average costs for milling wheat from the U.S., Canada and Australia gained more than 20 percent in the four months that ended on Dec. 31, government data show. The farm ministry, which sells to flour millers and reviews prices every six months, plans to announce a change next month, based on purchasing costs through February, Shirara Shiokawa, director at the ministry's grain trade division, said Jan. 19. He declined to elaborate.

World food prices climbed 25 percent last year to a record in December on higher sugar, grain and oilseed costs, according to the United Nations. The level exceeded that reached in 2008, when accelerating food prices sparked deadly riots from Haiti to Egypt. Companies such as Japan's largest flour miller, Nisshin Seifun Group Inc., and Yamazaki Baking Co. raised bread and noodle prices when the government increased prices in 2008.

"Rising wheat prices will boost food costs in Japan, upsetting consumers as they are struggling with a lack of pay increases amid deflation and high unemployment," said Chino, who heads the Tokyo-based grain trading company.

The government boosted selling prices in April 2008 by 30 percent on average, the biggest increase in 34 years. Japan, which imports almost 90 percent of its wheat, puts overseas purchases and domestic sales under state control to stabilize grain supply to consumers. The country imported 4.8 million metric tons in the year to last March 31.

Governments from Beijing to Belgrade are boosting imports, limiting sales or releasing stockpiles to curb food inflation. Food prices rose 9.6 percent in China in December, customs data show. Three people were killed and 420 injured in protests over milk and flour costs in Algeria this month.

In Tunisia, President Zine El Abidine Ben Ali tried to end a month of protests by promising lower prices for bread, milk and sugar, before handing over power to his prime minister on Jan. 14 and fleeing the country. Indonesia is the biggest importer in Asia.

Wheat may gain 16 percent this year, with sugar, corn, soybeans, coffee and cocoa also climbing, according to a Bloomberg survey of analysts, traders and investors in December.

Japan bought 852,000 tons of hard red winter wheat last fiscal year, or 18 percent of total imports, to make bread, Chinese-style noodles and dumplings. Futures on the Kansas City Board of Trade have gained 3.9 percent this month, extending last year's 59 percent rally.

Queensland's worst floods in 50 years have had limited impact on wheat shipments to Japan as the government has purchased the grain mainly from Western Australia, Shiokawa at the Agriculture, Forestry and Fisheries Ministry said.

Dry weather in Western Australia cut crop quality and quantity, forcing Japanese flour millers to change quality requirements to secure sufficient volumes from shippers, he said.

Japan bought 803,000 tons of standard white wheat from Australia last fiscal year mainly for production of Japanese-style noodles and cookies.

The government also purchased 159,000 tons of prime hard wheat grown in eastern Australia.

Japan raised selling prices on Oct. 1 for the first time in two years to an average ¥47,860 a ton, based on purchasing costs from March to August last year.