The European Union will raise the pressure in its raft of trade disputes with China, diplomats said Wednesday, with Brussels about to challenge Beijing's steel import duties at the World Trade Organization.

A European source in Geneva, home of the 159-nation WTO, said the formal complaint was due to be filed by the end of this week.

China and the EU are already locking horns over a range of trade issues, with Brussels having slapped tariffs on imports of Chinese solar panels.

In response, China has opened a probe into European wine imports, and is expected to take similar action against the auto sector.

Repeated claims by both sides of "dumping" -- selling goods at a cut price to grab market share -- have placed intense pressure on their huge trade relationship.

At the WTO, nations can ask the global body to decide whether fellow members are in breach of the rules of international commerce, and can be granted the right to impose retaliatory measures.

The EU is spotlighting Chinese tariffs on European stainless steel tube.

Japan has filed a similar steel case against China at the WTO, which in May set up a dispute settlement panel at Tokyo's behest.

In the past, the WTO has often folded multiple trade lawsuits against a specific member's measures into a single case.

The WTO's dispute settlement process can last for years due to the complexity of cases and the length of the various appeals.