Seoul officials have waited helplessly for Beijing to make a thorough investigation into the allegation by a South Korean activist that he had been tortured while in detention in China earlier this year for helping North Korean defectors. Their request for the improbable inquiry is just the latest in a series of cases that have made South Korea frustrated at China for disregarding or neglecting what they see as international standards.

But a string of seminars held here recently were flooded with calls for broader and closer economic cooperation between the two countries, which participants said would hold the key to South Korea’s continued growth.

Diplomatic observers say the renewed friction over historical and territorial issues between South Korea and Japan may push Seoul closer to Beijing, loosening the trilateral alliance the U.S. had sought to build with its two key allies against China, in which anti-Japan sentiment has also raged over a disputed island chain.

These situations testify to the increasingly complicated and multilayered ties between South Korea and China, which mark the 20th anniversary of establishing formal diplomatic relations today.

Over the past two decades, the two sides have seen their economic ties and personnel exchanges grow at a rapid pace hardly seen between any other two countries. According to figures from the Korea International Trade Association, bilateral trade volume jumped more than 34-fold from $6.38 billion in 1992 to $220.62 billion last year, with China having been the biggest export market for South Korea since 2003.

The number of visitors between the two countries skyrocketed nearly 50-fold from 130,000 to 6.4 million over the cited period, according to statistics from both governments.

Mainly reflecting the expansion of economic cooperation and personnel exchanges, they gradually enhanced ties from a friendly cooperative relationship in 1992 to a cooperative partnership in 1998, a comprehensive cooperative partnership in 2003 and a strategic cooperative partnership in 2008.

But the two sides have fallen short of building the political trust needed to cement their strategic partnership. They have seen ties frayed by disagreements over how to deal with North Korea’s provocative acts and defectors fleeing the impoverished North into China. Seoul has also been troubled by Beijing’s attempts to gloss over Korea’s ancient history and draw maritime borders to its advantage, as well as illegal fishing by Chinese trawlers.

For another two decades to come, the two countries will have to share the task of settling these frictions and bridging other differences to develop ties into a truly mature partnership.

To this end, South Korea needs to maintain a flexible and principled stance toward its much larger neighbor, while China is advised to concede Seoul’s initiatives on inter-Korean issues, departing from its adherence to geopolitical interests on the peninsula.

Close cooperation between Seoul and Beijing will be essential to persuading North Korea to move toward reform and openness and achieving the reconciliation and unification of the two Koreas. In this sense, South Korea will feel an increasing need to walk a fine line to ensure a strategic balance between China and the U.S., which are in escalating rivalry over hegemony in the Asia-Pacific region.

On the economic front, South Korea and China need to reach a free trade agreement as soon as possible in ways of maximizing mutual benefits to help overcome the increasing competition between their companies across nearly all major industries.

Both of the countries are set to change their leaders this year, with China opening a five-yearly Communist Party congress in October and South Korea holding presidential election in December. The new leaders will be given the crucial task of boosting ties between their countries to a higher dimension.