Japan will raise its tariff on imported refrigerated beef to 50 percent from the current 38.5 percent Aug. 1, despite strong opposition by the United States and Australia, government sources said Thursday.

The government will announce the tariff hike Tuesday after scrutinizing customs-cleared trade data for June due for release Thursday, the sources said.

The tariff increase will be effective until March 31, but the hike will probably not be applied to imported frozen beef, they said.

Imported beef in the April-June quarter increased by more than 17 percent from a year earlier, according to estimates by the public Agriculture & Livestock Industries Corp.

But the surge is in fact a return to normal levels after demand for imported beef plunged in the same period last year following the discovery of mad cow disease. , formally known as bovine spongiform encephalopathy.

Under a law introduced on the basis of World Trade Organization rules, Japan can automatically increase its beef tariff from 38.5 percent to 50 percent if there is a year-on-year increase of more than 17 percent in imports on a cumulative quarterly basis.

Japanese cattle breeders want the government to raise the tariff, but the move is opposed by the U.S. and Australia, including restaurant operators.

Pork imported in the April-June period is also estimated to have surpassed a level that triggers import curbs under a similar import-restriction system, the sources said.

If that is the case, the government-mandated basic import price will be raised and the gap between the price and import prices will serve as a tariff.