Aston Martin's new rival for the Porsche 911, codenamed AM305, will debut at the Detroit motor show in January - nearly 18 months before the £65,000 two-seater reaches showrooms.

The unexpected decision to give the smaller car an early world debut underlines its importance as the highest-volume model in Aston Martin's history.

The 4.2-litre V8 AM305 will be built at a new factory currently under construction in Gaydon, Warwickshire, pushing annual production up from 1500 to 5000 units by 2005.