DUBAI, Nov 8 (Reuters) - Dubai's Emirates airline renewed pressure on Sunday on European planemaker Airbus to upgrade its A380 superjumbo, saying it was ready to place an order as soon as the planemaker went ahead with an improved version of the world's largest airliner.

But the carrier's president, Tim Clark, said it could take another 6-12 months to make a decision on purchasing dozens of mid-sized jets while awaiting more in-service data on the recently introduced A350-900, which it is weighing against Boeing's 787-10.

Clark told reporters at the Dubai Airshow that Emirates has the option to convert the second half of its most recent order for current-generation A380s, which will be powered by Rolls-Royce, into the proposed A380neo, which could run on engines similar to those used on the Rolls-powered A350.

"We would like them to get on with it," Clark said, referring to the possible A380 upgrade, adding it did not necessarily need to be stretched despite recent reports that the double-decker could be enlarged to accommodate extra seats.

An A380neo could deliver 10-13 percent improved efficiency, he added.

(Reporting by Tim Hepher, Nadia Saleeem) ((tim.hepher@thomsonreuters.com; +33 1 49 49 54 52; Reuters Messaging: tim.hepher.thomsonreuters@reuters.net))