Toyota's upscale Lexus brand is set for a design shake-up as it battles to revive stodgy sales and a slipping image among young car buyers.

An edgier look will be on display this week, when Lexus lifts the wraps on a "concept" saloon, known as the LF-Gh, at the New York auto show.

Concept vehicles on display at car shows are often in the realm of fantasy, bearing little resemblance to later production models. But Mark Templin, Lexus's US chief, described the LF-Gh - short for Lexus Future Grand Touring hybrid - as "a new face on Lexus".

He said that "a lot of the design concepts in that vehicle will translate into a lot of the cars that we'll be launching in the next couple of years".

Interior features will also receive a facelift, including steering wheels, clocks and dashboard layout.

Lexus has held the number-one spot in the US luxury- vehicle market for the past 11 years, but fell behind both Mercedes-Benz and BMW in the first three months of this year.

It also faces growing challenges from Audi, Cadillac and South Korea's Hyundai.

While Lexus's January-March sales were 6.2 per cent higher than a year earlier, Audi gained 22 per cent and Cadillac 35 per cent. Hyundai's Equus is priced far below the comparable Lexus model.

Lexus's German rivals are launching smaller, sportier models. Mercedes will show a small A-Class concept at the New York and Shanghai shows this week, while BMW has announced plans for new models based on the Mini platform.

Mr Templin said increasingly stringent US fuel-economy and emissions rules were forcing Mercedes and BMW "to do things that we're not going to do". "We have this big sister division called Toyota that already does that," he said.

"We don't want to water down our brand by going down market too much. Small can still be luxurious, but it will be interesting to see whether people are willing to pay for expensive small cars."