Airbus announced the 18-month delay on the eve of the Paris Air Show, saying it would gain advantage in a battle for wide-body market share between the 365-seat Boeing 777-300ER and the future 350-seat A350-1000, now due in 2017.
A senior Boeing executive shrugged off the threat to the long-range 777-300ER, which will be displayed at the show.
We've always seen that plane as a little bit of a struggle, said Randy Tinseth, vice president of marketing at Boeing's commercial division.
The only change here is it's a little bit later, he said.
The A350 is being developed in three models of which the A350-1000 is the largest.
Tinseth was quick to point out strong demand for the 777-300ER. Boeing has 225 unfilled orders for the plane, according to its web site. Total sales exceed 500 planes.
In a direct stab at Airbus's design plans for the $12 billion project, Tinseth said Boeing believes the combination of wing and engine on the European plane is wrong.
Airbus is insisting that after a series of relaunches the A350 will offer what its customers want and that its lightweight materials will help it outperform the older and heavier 777.
Airbus sales chief John Leahy said top airlines had asked the European company to increase the range and payload of the A350-1000 which will now be able to tackle to emerging new routes like Paris to Santiago or Shanghai to Boston.
I think most of the world's airlines will be delighted with this airplane, Leahy said.
(Additional reporting by Geert De Clercq, Editing by Tim Hepher)