Insiders in the US are reporting that Apple may be working on an ultra-thin, large-screen laptop to slot into its lineup between the MacBook Air and MacBook Pro.

A report on MacRumors says the 15-inch product is already in late testing stages, and is expected to emulate the MacBook Air in its lack of an optical drive.

A corroborating report on TUAW agrees, saying the model will come under the MacBook Pro moniker, with a 17-inch version also under development.

"We might see them under Christmas trees, with a few weeks to spare,” the report adds.

Apple unveiled new versions of its MackBook Air models last week, at the same time as it launched its new operating system, OS X Lion.