The head of Boeing Co.'s commercial aircraft unit on Sunday backed a call by rival Airbus to work closely on producing more environmentally friendly planes, but said real progress was the responsibility of jet engine makers, rather than plane builders.

The questions you ask are more appropriately addressed by the engine guys than the airframe guys, the chief executive of Boeing's commercial plane unit said, when pressed on green issues at a briefing with reporters in Paris on Sunday. We're pushing the engine guys as hard as anyone else.

Boeing, along with other manufacturers and airlines, has come under the spotlight recently over the question of emissions and fuel efficiency. The issue is set to play a larger role than ever at the biannual Paris Air Show, which starts on Monday.

Carson's comments are a direct wake-up call to the world's leading jet engine makers, General Electric Co., Rolls-Royce Plc and Pratt & Whitney, a unit of United Technologies Corp.

The best thing the industry can do together is put pressure on the engine manufacturers to incorporate new technologies into the engines, Carson said.

Pollution was thrust to the top the aerospace agenda on Thursday when the president of Boeing's rival Airbus called for a high-level summit of engine makers and plane builders to give it the highest level of attention.

Airbus pledged that by 2020, all of its new aircraft will produce 50 percent less carbon dioxide and 80 percent less nitrogen oxides than in 2000.

Carson welcomed the call for attention, but said green issues were best handled by industry-wide bodies the International Civil Aviation Organization and the International Air Transport Association.

I'm absolutely delighted he sees the need the same way we do for us in the industry to work together to improve the efficiency and social responsibility of the products we bring into the marketplace, Carson said. If he (Gallois) wants to talk to us, we will always answer the phone.

Boeing reclaimed the title of the world's biggest-selling plane maker last year from Airbus, partly through strong sales of its new lightweight, fuel efficient 787 Dreamliner.

The Chicago-based company is outselling Airbus, a unit of European aerospace group EADS, 2-to-1 so far this year. Both are likely to announce new orders at the air show.