The United States on Tuesday formally filed two WTO complaints against China over so-called copyright piracy and restrictions on the sale of American books, music, videos and movies.

The U.S. trade delegation in Geneva has handed related documents to the World Trade Organization (WTO), formally setting in motion the WTO's dispute settlement procedure, a trade source said.

The Chinese mission to the WTO confirmed it had received the complaints and also a request for consultations from the U.S. side.

WTO dispute settlement procedures stipulate 60 days for consultations between the United States and China. If the consultations fail, the United States could ask for a WTO panel to investigate and rule on the dispute.

The two new cases represent the latest effort by the Bush administration to increase pressure on China in the area of trade despite Beijing's active efforts in cracking down on piracy.

In late March, the U.S. government announced its decision to impose penalty tariffs against the imports of Chinese coated free sheet paper, a decision altering a 23 year-old bipartisan policy of not applying the countervailing duty (CVD) law to China.

The Chinese Ministry of Commerce on Tuesday responded strongly to the latest U.S. move at the WTO, saying it "runs contrary to the consensus between the leaders of the two nations about strengthening bilateral trade ties and properly solving trade disputes."

"It will seriously undermine the cooperative relations the two nations have established in the field and will adversely affect bilateral trade," a spokesman said.