WASHINGTON (Reuters) - The United States is launching a World Trade Organization case against China over its export restrictions on raw materials, U.S. Trade Representative Ron Kirk said on Tuesday.

In Brussels, the European Union said it was joining the United States in the action, which follows failure to persuade China to reduce its export tariffs and raise quotas on materials such as zinc, tin, tungsten and yellow phosphorous.

“After more than two years of urging China to lift these unfair restrictions, with no result, we are filing at the WTO today,” Kirk told a news conference in Washington.

“We are most troubled that this appears to be a conscious policy to create unfair preferences for Chinese industries,” he said.

Kirk said the United States was formally requesting consultations with Beijing, the first step in the case. If those talks fail, the next step would be to request that a WTO panel hear the complaint, a step that can take years.

Western governments say resource-hungry China has continued to restrict exports of raw materials used in steel, semiconductors, aircraft and other products despite Beijing’s pledge to eliminate taxes and charges on exports when it joined the WTO in 2001.

The United States and other Western nations say these quotas and taxes hurt European and U.S. companies while giving Chinese companies an unfair advantage. But taking action at the WTO is expected to further damage already brittle trade relations with China.