BEIJING (REUTERS) - China's President Xi Jinping pledged to make concerted efforts with South Korea's President Moon Jae In to properly address differences between the two countries, the official Xinhua news agency said on Thursday (Aug 24).

Xi made the remarks in a congratulatory message sent to Moon on the 25th anniversary of the establishment of China-South Korea diplomatic relations, Xinhua said.

Development of China-South Korea relations makes a positive contribution to regional peace and development, Xinhua cited Xi as saying.

President Moon, in his message to the Chinese leader, assessed that their bilateral relations have seen significant advance and expressed hopes that the Seoul-Beijing ties that he cherishes will further develop into a "substantial" strategic cooperative one, according to South Korea's foreign ministry.

President Xi also said he regards China-South Korea relations as important, hoping that the two neighbours will "appropriately" deal with their differences and further advance the ties in a "stable and healthy manner," the South Korean foreign ministry said.

Since establishing formal diplomatic ties on Aug 24, 1992, the two countries have expanded cooperation in numerous areas. In particular, their trade have surged more than thirty-fold with human exchanges up nearly seventy-fold.

The ties, however, have been marred recently by the prolonged row over South Korea's decision last year to allow the deployment of the US missile defence system, known as Terminal High Altitude Area Defence (Thaad), on the Korean peninsula.

South Korea and the US claim that the Thaad system is aimed at countering missile threat from North Korea, China strongly objects to the deployment, saying that it the system's powerful radar will look deep into its territory and undermine regional security.

China has pressured South Korean businesses through boycotts and bans, such as ending Chinese group tours to South Korea and closing most of South Korean conglomerate Lotte Group's Lotte Mart retail stores in China.

Yonhap news agency reported that Hyundai Motor Co. and its affiliate Kia Motors Corp. still struggled last month in China, posting a 37 per cent on-year slump in their vehicle sales in the world's largest automotive market, industry data showed on Thursday.

In July, Hyundai Motor and Kia Motors sold a combined 70,017 vehicles there, down from 111,021 units a year earlier, the companies' data showed.

Chinese Foreign Ministry spokeswoman Hua Chunying said the exchange congratulatory messages was consistent with usual practice. Many tangible and mutual benefits had been delivered to people of both countries since the establishment of diplomatic ties, she told a daily news briefing.

"We hope the South Korean side can summarise and look back on the experiences and lessons from the 25 years of diplomatic relations and take constructive actions to appropriately address relevant sensitive issues and differences to improve relations between China and South Korea," Hua said.

"On the issue of THAAD, China's position is very clear, resolute and there is no change."

China Daily, in an editorial published on Thursday (Aug 24), urged Seoul to revive bilateral ties by reversing its decision to deploy Thaad.

"Thursday marks the 25th anniversary of diplomatic relations between China and the Republic of Korea, an occasion that should have been observed with lots of fanfare and the extending of mutual best wishes," it said.

Yet such high-profile celebrations are conspicuous by their absence, it added, and said that the absence can be attributed to the deployment of Thaad in South Korea.

President Moon has also pushed China, North Korea's most important ally and trading partner, to do more to rein in Pyongyang's missile and nuclear weapons programmes.

North Korea has conducted two nuclear tests and dozens of missile tests since the beginning of last year, significantly raising tension on the heavily militarised Korean peninsula and in defiance of U.N. Security Council resolutions. Two intercontinental ballistic missile tests in July resulted in a new round of tougher global sanctions.