Airbus fears that China is blocking an order for 10 more purchases of its A330 long-haul planes in reaction to a disputed European carbon tax, a source close to the company said on Wednesday.

Airbus parent company EADS said earlier this month that China was refusing to approve airline orders for the sale of 45 of its planes, including 35 A330s and 10 A380 superjumbos, because of the tax on aircraft emissions.

The source said a new order for the 10 purchases had not yet been approved by the Chinese government after weeks of waiting.

"The number of blocked A330s could rise to 45," the source said.

The carbon tax imposed on airlines by the European Union came into effect on January 1, but carriers will begin receiving bills only in 2013 after this year's carbon emissions have been assessed.

The EU says the tax will help it achieve a goal of cutting carbon emissions by 20 percent by 2020 and that it will not back down on the plan.

But more than two dozen countries, including China, Russia and the United States, have opposed the EU move, saying it violates international law.

A senior Chinese diplomat said this week that it "makes sense" for Chinese airlines to shun aircraft made in Europe because of the tax.

The Wall Street Journal reported that the new Chinese ambassador to the EU, Wu Hailong, told reporters that a decision by the EU to make non-European airlines subject to the tax "contributed to the current dilemma."