(REUTERS) - Airbus has stopped delivering A320neo jets powered by Pratt & Whitney's geared turbofan engines and halted pre-delivery test flights after the latest technical hitch to affect the supplier, two sources familiar with the matter said.

A European safety bulletin, effectively grounding aircraft that have already been delivered with two engines from the same suspect batch, affects about 15-20 aircraft already in service,, they said.

Airbus has briefed airlines and leasing companies on the problem and cannot yet say how long it will take to resolve, one of the sources told Reuters on condition of anonymity.

An Airbus spokesman said the plane maker is "in discussions with customers about delivery schedules".