China formally announced it will impose emergency three-year curbs on foreign steel imports beginning Wednesday.

The so-called safeguard tariff measures invoked under World Trade Organization trade rules will apply to five categories of steel products, including hot-rolled steel sheets and cold-rolled stainless sheets, China's Ministry of Foreign Trade and Economic Cooperation said Tuesday.

The measures comprise an extension of preliminary steel tariffs Beijing adopted May 24.

China says the tariffs are necessary to compensate for the U.S. imposition in March of three-year tariffs of up to 30 percent on an array of steel imports. The U.S. tariffs are designed to aid the ailing U.S. steel industry.