South Korea's foreign minister said Monday that a recent deal between North Korea and Japan is feared to hamper cooperation among Seoul, Washington and Tokyo in resolving the issue of the North's nuclear weapons program.

In late May, North Korea and Japan agreed to re-investigate the fate of Japanese nationals kidnapped by Pyongyang decades ago. In return, Japan promised to ease some of its unilateral sanctions on Pyongyang and give humanitarian aid to the reclusive country "at an appropriate time."

"(The Korean government) does not exclude the possibility that (the Pyongyang-Tokyo deal) may develop in a way that deepens concerns about trilateral coordination (over North Korea's nuclear issues)," Foreign Minister Yun Byung-se told lawmakers.

When asked whether the Japanese government has given a sincere explanation to Seoul, Yun hinted that consultations between the two countries over the issue have not gone smoothly.

Yun also renewed his pledge to counter Japan's review of its 1993 key apology admitting to the coercion of its wartime sexual slavery during World War II.

"The government plans to sternly deal with any of Japan's attempts to roll back the wheels of history," he added.

As for whether Korea is mulling joining a China-led infrastructure bank, Yun said that related government agencies are studying such a possibility, but it is not clear whether the agenda will be discussed at the upcoming summit among the leaders from Korea and China.

Chinese President Xi Jinping is scheduled to make a two-day visit to Seoul later this week to meet South Korean President Park Geun-hye.

Some media have reported that Xi may bring up the issue of requesting Seoul join the Asia Infrastructure Investment Bank, which he proposed last year with an aim at helping Asian countries build infrastructure.

China has excluded the U.S. and Japan for the envisioned development bank. (Yonhap)