The government is set to accuse South Korean and Taiwanese companies of exporting polyester staple fiber to Japan at unfairly low prices and levy antidumping duties on their imports, government sources said Tuesday.

It would be the first time in more than six years for Japan to impose tariffs ostensibly to counter dumping. Japan has levied antidumping duties twice in the past, the last time being in August 1995 on cotton yarn imports from Pakistan.

The Ministry of Economy, Trade and Industry and the Finance Ministry, which have jointly studied the issue over the past year, are expected to inform South Korea and Taiwan by mid-April of Japan's decision on the duties, the sources said.

If the government imposes the duties, which would probably happen in late May at the earliest, they would be levied for a maximum of five years, they said.

Tokyo launched a probe last April into imports of the fiber after five Japanese textile firms, including Toray Industries Inc., asked the government to impose antidumping measures in light of a rising number of cheap imports. Polyester staple fiber is used to make carpets and stuff quilts.

According to METI and the Finance Ministry, the South Korean exports were 32.5 percent cheaper on average than local goods in 1999 and 2000, and Taiwan's fiber was 8.8 percent less expensive.

The Japanese manufacturers said they lowered the price of their polyester staple fiber 13 percent between fiscal 1997 and 1999, while their sales slipped 8 percent.

The United States and the European Union have already imposed antidumping duties against imports of polyester staple fiber from South Korea and Taiwan.