GENEVA — The European Union said yesterday that it has asked to participate in World Trade Organization talks over Chinese copyright and trademark policy initiated last month by the United States.

Mexico also is requesting to join the dispute as a so-called "third party," the WTO said. The procedural step, which already had been taken by Japan and Canada, signifies growing international pressure on Beijing to crack down on product piracy.

"This is a case of great importance," said Peter Power, spokesman for EU Trade Commissioner Peter Mandelson. "We have asked to be third parties."

The EU is China's largest trading partner.

The United States filed two new cases against China at the WTO on April 10, challenging Beijing's rules for copyright and trademark protection, as well as its alleged failure to remove import and distribution restrictions on copyrighted U.S. goods including newspapers, magazines and video games.