Japan has notified the World Trade Organization of its intention to join as a third party the United States' complaint against China over alleged theft of intellectual property, a source has said.

If China and the United States approve Japan's participation, Tokyo would be able to express its views in the WTO consultations, the source said Friday.

As part of retaliatory measures against China, the Office of the U.S. Trade Representative launched the complaint on March 23, saying China uses discriminatory licensing requirements to compel the transfer of technologies from U.S. companies to Chinese firms.

China appears to be breaking WTO rules by denying foreign patent holders, including U.S. companies, basic patent rights to stop a Chinese entity from using the technology after a licensing contract ends, the USTR said.

In recent years, Japan has been concerned by the same issue, and it also has huge stake in the matter, according to Japan's notification sent to the WTO.

If Japan's participation is accepted, Tokyo is set to say that the Chinese measure regarding technology transfer is distorting the competitive environment between companies, the source said.

The European Union will also seek to join the consultations as a third party, rather than jointly filing the complaint with the United States, the source said.

Under the WTO dispute settlement process, the United States and China will first consult over the issue. If they fail to reach a solution, the United States may request the establishment of a WTO dispute settlement panel to review the matter.