* All-new A4 to debut at Frankfurt auto show on Sept. 14
* A4 to lag behind BMW, Mercedes model sales 2014-2020 -IHS
By Andreas Cremer
BERLIN, July 27 (Reuters) - Audi hopes that the redesigned top-selling A4 saloon will shore up its fortunes in China where the premium brand is grappling with dwindling sales and a leadership change.
Global carmakers have come under pressure to raise their game in the world's biggest auto market where an anti-corruption drive, a slowing economy and tumbling stocks are weighing on sales.
Volkswagen's flagship division will court Chinese buyers with a lighter and more fuel-efficient version of the A4, which last year added a fifth to Audi's global output of 1.8 million cars, Audi product manager Jens Kotnik said.
"The A4 is a crucial pillar of our global growth strategy," Kotnik said in an interview. "It's a key model for Audi, especially in our main markets China, Europe and North America."
Ingolstadt, Germany-based Audi has a goal to wrest the luxury-sales crown away from BMW by the end of the decade, in a three-way contest that also includes Mercedes-Benz .
The all-new A4, which will be unveiled at the Frankfurt auto show in September and go on sale in Europe in November, will compete with an upgraded version of BMW's entry-level 3-Series and a redesigned Mercedes C-Class that came to market last year.
But after a decade of steady growth, Audi is facing headwinds in China where Germany's leading premium brands earn 30-50 percent of their profits.
VW's main earnings contributor is reviewing a 2015 target of delivering 600,000 cars in China. Volume growth has slowed sharply since December and fell 5.8 percent in June.
Audi, due to publish an updated Chinese sales goal on Thursday with first-half results, said last week it was replacing its regional top executive though denied that the move was triggered by falling sales.
But with indigenous brands such as Beijing Auto, Dongfeng and BYD Co. pushing deliveries in the hard-fought midsize segment, Audi's core model may struggle in China, research firm IHS Automotive found.
His estimates A4 sales in China will rise by only 2 percent to 124,866 saloons and station wagons by 2020 from 122,407 last year. It sees a 6.7 percent gain to 103,762 units for BMW's 3-Series and a 61 percent jump to 58,632 for the C-Class which Mercedes started making locally in 2014.
"New product is key but gives no assurance in the hard-fought Chinese market," said Stefan Bratzel, head of the Center of Automotive Management think-tank near Cologne.
Editing by Jason Neely