A European envoy held out a possible compromise in a dispute with China over emissions charges on airlines, saying Europe might alter its system if Beijing helps to negotiate a global agreement on controls.
China, India, the United States and Russia oppose European emissions charges on airlines that took effect on January 1. Beijing has barred its carriers from cooperating and has suspended purchases of European aircraft to press its objections.
Talks on a global emissions system have begun in the International Civil Aviation Organization, a UN body, said Matthew Baldwin, the European Union director of aviation.
He said the EU might alter its Emissions Trading System if an agreement is reached.
"We would very much like to see a stronger role played by China in those talks," Baldwin told reporters at a European-Chinese aviation conference.
"In the event of a global solution in ICAO, the EU is fully ready to review and amend the ETS directive to take account of that global solution."
Baldwin said he would press that appeal during talks this week with China's planning agency, the National Commission for Reform and Development, and aviation regulators this week.
Baldwin said the ICAO talks are looking at four possible "market mechanisms" to regulate carbon emissions but gave no details.
The dispute highlights the complex status of countries such as China and India that are large emissions sources but as developing economies are exempt from mandatory limits.
China has promised to curb emissions but has rejected binding commitments. The communist government warned in February it would take steps to protect its carriers.
In March, European aircraft manufacturer Airbus Industrie said Beijing was blocking orders by China's state-owned carriers for jets with a total list price of $US12 billion ($A12.29 billion), in a challenge to the carbon charges.
Airbus said it also is seeing "retaliation threats" from 25 other countries.
Beijing has leverage in a dispute because its airlines carry large numbers of Chinese and other Asian tourists to Europe. Any disruption would hurt Europe's travel industry at a time when the continent is struggling with a debt crisis and high unemployment.
India also has barred its carriers from paying the European charges, which the EU will start to collect next year.
Under the European system, airlines flying to or from Europe must obtain certificates for carbon dioxide emissions.
They will get free credits to cover most flights this year but must buy or trade for credits to cover the rest.
Baldwin declined to say whether Chinese or other airlines might face penalties if they refuse to cooperate.
"We obviously hope that everyone will comply with the emissions trading system, and I think it is far to early to start talking about punitive measures," he said.
China rejects the charges as an improper tax. It filed a legal challenge along with US airlines and India.
The EU's highest court upheld them in December, ruling they were not a tax because airlines could be exempt if they take "equivalent measures" to curb emissions and can recoup money through trading credits.
Environmentalists welcomed the European program, one of the most far-reaching measures to regulate greenhouse gas emissions.
Although only three per cent of total carbon emissions come from aircraft, aviation is the fastest-growing source.
EU officials have defended the charges as consistent with Europe's determination to be a leader in curbing climate change. They say that with free credits taken into account, the added cost per passenger on a flight from Beijing to Brussels, the EU capital, would be 17.50 yuan or 1.90 euros ($US2.70).
The International Air Transport Association, an industry group, opposes the European charges and has appealed for a global settlement.
IATA represents about 240 airlines that carry 84 per cent of global air traffic.
IATA says the European system will cost airlines up to 900 million euros ($A1.23 billion) this year and rise to 2.8 billion euros in 2020.
