With bodywork extended by 125mm (five inches), the range-topping Long Wheelbase will be the longest model in the luxury saloon sector when it goes on sale in the autumn.
Aston Martin, Jaguar and Land Rover North America president Mike O'Driscoll told Fleet News: 'This is a hugely important car for us and we expect it to account for more than half the global XJ volume.
'The fact that eight out of every 10 cars we make will be sold in the US makes it vital we give it maximum exposure in this market.'
Developed to offer more effective competition to Mercedes-Benz and BMW in the limousine sector, the wheelbase of the LW is 125mm longer and its roofline is 7mm higher.
O'Driscoll added: 'The clever thing is that while it doesn't appear any bigger from the outside, this car provides 39 inches of legroom for rear seat passengers. And because it weighs only 24kg more than the standard car, there are no penalties on economy, emissions and performance.
'Our vehicle is easily the lightest in the class. Its aluminium construction gives us an advantage of about 100kg over our nearest rivals, so it has all the agility and driving dynamics that have already won praise for the standard version.
'We're setting fresh standards, and with the very aggressive pricing strategy we're planning, this is a no-compromise Jaguar with terrific potential.'
Customers will be offered a choice of four rear seating configurations, including fixed or power-adjustable bench layouts and individual powered and heated seats separated by a centre console with additional storage space.