"Boeing have asked us for proposals, we've produced some proposals. They'll continue to refine their requirements and we'll continue to see if we can address those requirements economically," Warren East told reporters.

Boeing is studying a gap between narrowbody jets and long-haul aircraft for a potential new mid-market airplane that could seat 220 to 260 passengers. Currently Rolls-Royce is focussed on supplying engines to wide-body jets.

"As we all know there's question marks about whether they're actually going to go ahead or not," East added.

Chris Cholerton, Rolls-Royce's civil aerospace president, said problems with Rolls's Trent 1000 engine which had left some Boeing 787 Dreamliner planes grounded would not prevent it from providing the engine for the new plane being mooted.

"I absolutely don't see it (Trent 1000) as a barrier to success on NMA," he said, referring to the industry's term for the new mid-market airplane (NMA).

(Reporting by Sarah Young; Editing by Mark Potter)