PARIS - Airbus has shelved studies aimed at improving its A320neo family, designed to fend off a mid-market jet that Boeing hopes to build, two people familiar with the matter said.

The surprise decision to back away from the proposed "A320neo-plus" and "A321neo-plus," which would lengthen and modernize both models, comes as Airbus continues to face problems in securing increases in current A320neo output.

"The ramp-up is not going as well as hoped," a person with knowledge of the supply chain said. Another said Airbus had declared industrial matters top priority amid engine shortages, calling off plans to show the A320neo-plus design to airlines.

"We do not comment on product policy," an Airbus spokesman said, asked about a decision to halt work on the A320neo-plus.

The advanced study was one of the items awaiting new planemaking chief Guillaume Faury when he replaced Fabrice Bregier in February, alongside engine supply problems that have forced the company to suspend deliveries of some A320neo jets.

In that climate, and with a new planemaking management still finding its feet, Airbus is adopting a more cautious attitude to risks and focusing on ramping up production as smoothly as possible to defend its main source of profits, the people said.

(Reporting by Tim Hepher; Editing by Luke Baker)