The foreign ministers of South Korea and China held bilateral meetings in Seoul on Saturday, but Beijing did not bring up the controversial issue of Washington's possible deployment of an advanced U.S. missile-defense system on Korean soil, a Seoul official said.

The meeting between South Korean Foreign Minister Yun Byung-se and his Chinese counterpart, Wang Yi, came as Seoul's diplomacy has been put to the test amid a mounting Washington-Beijing row over a Terminal High-Altitude Area Defense (THAAD) battery and a China-led Asian development bank.

The Seoul-Beijing talks, which were held on the sidelines of a meeting of foreign ministers from Seoul, Beijing and Tokyo, came as China has explicitly voiced opposition against Washington's move, apparently out of concerns that it may be aimed at containing a rising China.

"THAAD was not an agenda item for the talks, so there was not any consultation over the issue," a ranking official at Seoul's foreign ministry told reporters.

South Korea is struggling to walk a diplomatic tightrope between the U.S., Seoul's key ally, and China, Seoul's largest trading partner, over the sensitive security issue.

China has recently ratcheted up its concerns over the possible THAAD deployment even though Seoul and Washington said there have been neither consultations nor any decision on the issue.

Liu Jianchao, the Chinese assistant minister of foreign affairs, urged South Korea on Monday to take heed of Beijing's concern over the possible THAAD deployment in South Korea.

A day later, Seoul's defense ministry urged neighboring countries not to try to influence its decision on the THAAD deployment in what could be its thinly-veiled criticism of China's pressure against the move.

The Chinese foreign minister expressed hope that South Korea will join the China-led Asian Infrastructure Investment Bank (AIIB) during the talks, according to the Seoul official.

China launched the AIIB late last year with other 20 nations as a counterbalance to the Asian Development Bank, which is dominated by the U.S. and Japan.

South Korea plans to decide soon whether to join the AIIB, while the U.S. has apparently pressed Seoul not to invest in the regional bank out of concerns over China's bid to increase its economic clout.

China also extended an invitation to South Korean President Park Geun-hye to attend Beijing's commemorations to mark the 70th anniversary of the end of World War II, according to Seoul's foreign ministry.

Following his talks with Wang, Yun held talks with Japanese Foreign Minister Fumio Kishida, during which they agreed to make efforts to improve their strained bilateral ties in this landmark year.

"The two sides agreed to make progress over ongoing bilateral talks on the issue of Japan's wartime sex slaves," Seoul's foreign ministry said.

This year marks the 50th anniversary of the normalization of the diplomatic ties between South Korea and Japan. But Japan's refusal to face up to its wartime atrocities has sparked a diplomatic tension between the two.

Last April, Seoul and Tokyo launched talks on Japan's sex slavery, but no breakthrough has been made due largely to Japan's attitude.

A Seoul official said Monday that the two sides "went beyond" the repetition of their respective stances at the latest talks.

But experts said there is a long way to go as speculation is growing that Japanese Prime Minister Shinzo Abe will not include words of apology for Japan's past atrocities in his new statement due out in August to mark the 70th anniversary of the end of World War II.

Since taking office in early 2013, President Park has shunned a bilateral summit with Abe, calling on Japan to first sincerely apologize for the sex slavery issue. (Yonhap)