Airbus is studying whether there is demand for a larger member of its A350 jet family and expects to make up its mind within a couple of months, its sales chief said on Monday.

The European planemaker is not yet offering a specific design to airlines, but anything that it does decide to build would leapfrog Boeing's 777X, he said, referring to a new 406-seat version of the US company's 777 wide-body series.

Airbus's largest twin-engined jet is the 369-seat A350-100, which competes partly with the 365-seat Boeing 777-300ER.

Asked about speculation that Airbus could build a larger version of the A350, sales chief John Leahy told Reuters, "We don't know yet. If I had to bet, the larger part of the market will stay around the A350-1000 or 777-300ER size category.

"I think in the next couple of months we will know if we want to do something."

Speaking to Reuters on Sunday, Airbus planemaking chief executive Fabrice Bregier did not rule out expanding the A350 family, but said this was not an immediate priority .

In a sign that any new plane would need to be carefully marketed so as to avoid upstaging the existing A350-1000, Leahy denied that the potential new plane would be called the A350-1100.

"There is nothing called the A350-1100 and I wouldn't call anything the 1100," he said.

Boeing launched its 777X with record orders at the last Dubai Airshow in 2013.

The move was widely seen as clipping the wings of the A350, which was designed partly to erode a monopoly enjoyed by the 777-300ER at the top end of the lucrative wide-body market.

Industry sources have said Airbus is studying a counter-move to expand its new A350 family with over 400 seats and power it with the next generation of Rolls-Royce engines.

Leahy said any new plane would be more than a simple effort to plug the gap with the 777X.

"It would be sitting right on top of them with similar range and payload and substantially lower seat-mile costs. But before putting our resources into that, we have got to determine if that is a big enough market."

"If the market (for) 40-50 more seats is large enough, we don't necessarily want to give that whole thing to Boeing."

He said any new plane would have "double-digit better" operating costs per seat than Boeing's in percentage terms. - Reuters