The European Union refused Thursday to back down from a disputed airline emissions fee despite China's refusal to pay the new charge to land in Europe.
The 27-nation EU began to require all airlines to buy pollution permits to fly to Europe on January 1 despite stiff opposition from the United States, China and many other countries.
Some airlines have started to pass the cost on to their passengers.
"We are not modifying our law and we are not backing down," Isaac Valero-Ladron, spokesman for EU climate action commissioner Connie Hedegaard, told a news conference.
"It's like if the Chinese want to do business in Europe, like open a restaurant or something, they have to comply with the health and safety requirements. This is not that different," he said.
"If you want to operate in Europe you have to respect the law, you have to respect the environmental law."
The China Air Transport Association, which represents the country's airlines, warned that Chinese carriers would not pay the charge.
The EU system calls for fines of 100 euros per tonne of CO2 against companies that refuse to comply, or a flight ban as a last resort. The current market price for one tonne of CO2 is around 7.0 euros.
But Chinese airlines are unlikely to be penalised immediately as carriers have until April 30 next year to calculate their annual emissions and buy polluting rights for 2012.
Under the EU's Emissions Trading System (ETS), airlines will have to buy 15 percent of polluting rights accorded to them in 2012 -- the 15 percent is estimated at 32 million tonnes per year of CO2 by the European Commission. The measure could bring in 256 million euros this year.
Despite their objections, US and Chinese airlines have applied for the 85 percent of allowances that are handed out for free, Valero-Ladron said.
The EU, the only region in the world to make airlines pay for emissions, says it will provide exemptions to air carriers from nations that enact similar measures to reduce airborne pollution.
"If any country wants to reduce emissions differently, that is fine with us as long as their measures have an equivalent environmental impact," Valero-Ladron said.
He said the Commission was involved in talks with countries over the issue.
The 27-nation bloc decided to include airlines, responsible for three percent of global emissions, in the ETS in the absence of a global agreement to cap aviation emissions.
The rules came into force on Sunday after the EU's highest court last month rejected a challenge brought by North American carriers, which had argued that it amounted to a tax and violated international aviation laws.
Foreign airlines and governments are still fuming.
Chinese foreign ministry spokesman Hong Lei urged the EU authorities to "resolve this issue in a pragmatic and prudent manner."
Some airlines have announced new ticket fees since the EU's rules came into force.
US carrier Delta Air Lines, one of the world's biggest airlines, added a $6 surcharge for two-way flights between the United States and Europe.
Germany's Lufthansa indicated it would raise its fuel surcharge, a move taken by Belgian carrier Brussels Airlines, which increased it by 10 euros to 135 euros for international flights and by three euros to 39 euros for EU routes.
The European Commission argues that the cost for airlines is manageable, estimating that the scheme could prompt carriers to add between 4.0 and 24 euros ($32) to the price of a two-way long-haul flights.
A one-way flight between New York and London emits around 385 kilogrammes of CO2 per passenger, a cost of around $5.40 per passenger at current carbon prices of 12 euros per tonne, according to Valero-Ladron.
Since airlines are only required to pay for 15 percent of their allowances, with 85 percent handed out for free, the actual cost would be between $1 and $2, he added.
"This is hardly an insurmountable issue for them," he said.