When asked about the complaint and counter complaint filed at the WTO by the United States and the European Union over state support to the aircraft makers, Supachai said the private sector was behind many of the recent bruising disputes between major trade powers.

"It's at the level of the private sector that most of these disputes are here. You're talking about Boeing, this is a private sector initiative, it's not because of Zoellick and Lamy," Supachai said, referring to the top US and EU trade officials.

"I hope the private sector will have a constructive attitude," Supachai told journalists, adding that private companies had the power to determine "how factionalised" the multilateral trade system could be.

Tensions over the end of textile import quotas in 2005 were fuelled by pressure from private industry, the WTO director general said, also pointing to the confrontation between the US and EU over steel, and others over subsidies.

"All these disputes are mainly because of a lack of adjustment by the private sector," the WTO director general said.

"If they are willing to take up the difficult and painstaking adjustments, probably with the help of governments, then we can avoid quite a number of disputes," he added.

Companies should turn to arbitration and consultation between themselves before they lobby governments for litigation, Supachai said.

The United States and EU are due to discuss their dispute over state subsidies to Airbus and Boeing at the WTO on Thursday and Friday.

On October 6, Washington lodged a complaint against European plane development subsidies to Airbus with the WTO, triggering a tit-for-tat European objection to indirect US subsidies for Boeing.

A senior Boeing official has said the WTO's procedure could also be the venue for fresh US-EU negotiations on revamping a 1992 transatlantic aircraft subsidies accord.