He seems to be moving away from his earlier careful approach, gradually showing his true colors ahead of a two-day South Korea-US summit in Washington from Thursday.

If Seoul makes a clear diplomatic policy shift after the change of government, that would affect not only the two countries' relations but also the three-way cooperation also including Japan, the observers said.

On Monday, Chief Cabinet Secretary Yoshihide Suga expressed displeasure at Moon's conciliatory attitude toward North Korea. Moon has proposed forming a joint team of South and North Koreans to compete in the 2018 Pyeongchang Winter Olympics.

"We don't know the details at all," Suga said. "I shouldn't comment on the matter."

Over Korean comfort women who were forced into prostitution for Japanese troops in wartime, Moon has said Japan is not making enough efforts.

Moon has also said the core to resolving the comfort women issue is that Japan should take legal responsibility and make an official government apology.

Tokyo has protested each time Moon made such remarks.

During his presidential election campaign, Moon pledged to renegotiate the 2015 bilateral agreement to resolve the comfort women issue.

But after his inauguration last month, he kept silent on the issue. Even during his first telephone talks with Abe, Moon did not mention the proposed renegotiations. (Jiji Press)