SEOUL (Reuters) - South Korea's Hyundai Motor Co (>> Hyundai Motor Co) dialled back on the edgier designs that helped it win market share abroad five years ago, launching on Tuesday a toned-down, angular version of its popular Sonata sedan to appeal to conservative drivers at home.

Hyundai, the world's fifth largest car maker with its Kia Motors Corp (>> Kia Motors Corporation) affiliate, is banking on the first restyling of the mid-size sedan since 2009 to help reverse a slowdown in sales and revenue growth, as it battles competition from foreign rivals at home and a slide in reliability rankings in the United States, its second-biggest market after China.

The company posted its first year-on-year fall in quarterly revenue in nearly three years in the fourth quarter of last year and forecast its global sales growth would slow to 4 percent in 2014 from 7 percent in 2013.

Automotive industry experts said the revamped Sonata looked more like the mid-sized Camry sedan by Hyundai's Japanese rival Toyota Motor Corp (>> Toyota Motor Corp). The car, which Hyundai has been making since 1985, will go on sale in March in South Korea and later in the United States.

"Hyundai has followed Camry in adopting a bland design," said a person who has close professional links with Hyundai and who declined to be named as he is not authorised to speak to the media.

"U.S. consumers are now used to the Sonata's distinctive styling and it will be challenging for the new Sonata to stand out in the U.S. market."

Hyundai officials appeared to acknowledge that the redesign could face hurdles in the United States. Design executive Juh Byung-chul told Reuters that U.S. consumer tests showed the new design was "good enough" and "acceptable."

The Sonata is Hyundai's second top seller after its Elantra model in the United States and Korea. The current model, with its distinctive curvy design, took the United States by storm when it was introduced five years ago, helping Hyundai to almost double sales to 230,605 in three years.

Sales of the current Sonata, however, fell in Korea to 89,400 in 2013 from a peak of 152,023 in 2010, a factor that prompted company chairman Chung Mong-koo and top management to push for more conservative redesign for the new model.

Hyundai said it aims to sell 4.9 million vehicles this year, although it did not disclose pricing and sales targets for the new Sonata.

Korea has become an increasingly important market for Hyundai as it fights against a rising tide of imports, with the likes of Germany's Volkswagen AG (>> Volkswagen AG) benefiting from free trade deals that cut tariffs.

"The new Sonata is key for Hyundai to restore sales and reputation at home and abroad," said Lee Sang-hyun, an analyst at NH Investment & Securities.

(Reporting by Hyunjoo Jin; Editing by David Chance and Miral Fahmy)

By Hyunjoo Jin