Photo/IllutrationPrime Minister Shinzo Abe, left, shakes hands with U.S. Vice President Mike Pence on Feb. 9 at a reception hosted by South Korean President Moon Jae-in, center. (Takeshi Iwashita)

PYEONGCHANG, South Korea--Japanese government officials are showing increasing concern as South and North Korea move closer toward engaging in discussions at the highest levels.

"In the past, both Japan and South Korea have gone along with conciliatory policies proposed by North Korea, but the only result has been to allow North Korea to continue with its nuclear weapon and ballistic missile development programs," Defense Minister Itsunori Onodera told reporters in Saga Prefecture on Feb. 10.

Onodera made his remarks in the wake of reports out of Pyeongchang, where the Winter Olympics are being held, that South Korean President Moon Jae-in had been invited to visit North Korea for direct talks with North Korean leader Kim Jong Un.

"It is inconceivable that Moon would visit North Korea when Pyongyang has shown no signs of specific action toward denuclearization," said a high-ranking Japanese Foreign Ministry official.

Government officials are especially concerned because a major reason for having Prime Minister Shinzo Abe attend the Opening Ceremony of the Pyeongchang Winter Olympics was to hold a meeting with Moon in which Abe reiterated the importance of continuing to maintain pressure on North Korea through coordination between Japan, South Korea and the United States.

But concerns about the future of such cooperation led to efforts over the past few days to demonstrate the strong ties between the three nations.

According to sources knowledgeable about Japan-U.S. ties, immediately after Abe met with Moon on Feb. 9, U.S. officials requested and were granted a hurriedly called meeting between Abe and U.S. Vice President Mike Pence, who was also in Pyeongchang to take in the Opening Ceremony. That meeting was held on top of a Feb. 7 meeting in Tokyo between Abe and Pence.

Moreover, the two further discussed what steps could be taken by Japan and the United States during the drive to a reception hosted by Moon. Pence invited Abe to ride with him to the reception site, sources said.

"There will be a need for Japan and the United States to work closely to continue to remind South Korea that it should not move any closer toward North Korea," a Japanese government source said.