* Audi January sales up 10.3 pct to 137,700 cars
* Lead over Mercedes may widen through 2020 -IHS
* BMW sales expected later this week (Adds Audi comment, IHS outlook and peer comparison)
BERLIN, Feb 9 (Reuters) - Audi outsold Mercedes-Benz in January as demand in China and the United States helped Volkswagen's flagship division post record sales and analysts said the lead over its German rival may widen.
Audi said on Monday sales rose 10 percent last month to 137,700 cars and sport-utility vehicles with the world's two largest car markets and Germany all posting double-digit gains.
Audi sold 15 percent more vehicles in China, its No. 1 market, even though overall demand there is slowing, and managed 4.7 percent growth in Europe despite a 13 percent slide in Russia.
"We have made a good start to the year although global economic uncertainties remain considerable," Audi sales chief Luca de Meo said, adding that January sales laid the ground for another increase in volumes this year.
With overhauls of its top-selling A4 saloon and the flagship Q7 SUV coming to dealerships this year, and more SUV offerings in the pipeline, Audi's advantage over Mercedes may expand to 178,000 cars by 2020 from 136,000 last year, research firm IHS Automotive said.
By comparison, the gap between the top-selling luxury car maker BMW and Audi may widen to 92,000 vehicles from 69,000, IHS said, leaving the pecking order in the three-way German contest unchanged.
Audi said January sales benefited from strong momentum for the enhanced A3 compact series and the revamped TT sports car.
Mercedes last Friday posted record sales of 125,865 models in January, a 14 percent gain from a year earlier.
BMW is expected to publish its January deliveries later this week. (Reporting by Andreas Cremer; Editing by Christoph Steitz and David Clarke)