The government is keeping mum on a secret visit to North Korea by one of Prime Minister Shinzo Abe’s advisers after Pyongyang revealed it to the United States and South Korea.

We “can’t reasonably explain” the visit because it was supposed to be kept secret, a government source said. Tokyo has been working with Washington and Seoul to get Pyongyang to drop its nuclear and missile threats.

Some observers are speculating that Japan was duped by a North Korean ploy aimed at undermining international efforts to put pressure on it. Footage of the adviser, Isao Iijima, meeting with North Korean officials was aired on TV right from the beginning of his trip.

Iijima, the man credited with engineering Junichiro Koizumi’s successful stint as prime minister and who is now masterminding Abe’s slick PR team, entered Pyongyang on Tuesday and returned to Tokyo on Saturday.

He was apparently dispatched to address the abduction issue, in which North Korean agents kidnapped Japanese nationals in the 1970s and 1980s. The issue is one of Abe’s biggest political priorities.

Chief Cabinet Secretary Yoshihide Suga has been using vague language to express Tokyo’s plan to relay developments in Japanese-North Korean relations to Washington and Seoul in some fashion.

“We will have state-to-state affairs judged through negotiations and meetings,” he said Thursday.

The United States and South Korea have clearly been less than pleased with Japan’s move. Seoul called Iijima’s excursion “not helpful,” given the need to coordinate with its two allies on North Korean issues.

Glyn Davies, the U.S. special representative for North Korea policy, signaled displeasure with the trip Thursday, telling reporters in Tokyo that he hadn’t heard about it and that little, if any, coordination had taken place between Tokyo and Washington beforehand.

South Korea’s criticism drew a curt reaction from Suga.

“I don’t understand what (Seoul) wants to say,” he said.

The negative reactions from Seoul and Washington are a sharp reminder that Japan, the United States and South Korea were united in their efforts not to hold dialogue with North Korea for the sake of holding dialogue unless Pyongyang clearly signals it is willing to return to the denuclearization issue.

The logic is that the three would be viewed as giving after-the-fact approval to North Korea acquiring nuclear weapons if they easily agree to hold dialogue with the hermit state.

The apparent lack of coordination was laid bare Tuesday when North Korea reported Iijima’s arrival through the media, showing the adviser shaking hands with North Korean officials at an airport.

On Thursday, the North’s official Korean Central News Agency reported that Iijima met with No. 2 leader Kim Yong Nam in Pyongyang. Kim is president of the Presidium of the Supreme People’s Assembly, North Korea’s legislature.

The revelation has made it difficult for Abe’s government to conduct behind-the-scenes negotiations with North Korea to resolve the abduction issue, some observers say.

By contrast, it has “enabled North Korea to proclaim to the world that it is not isolated in the international community,” a Foreign Ministry source said in Tokyo.

“With the otherwise secret North Korean visit by Mr. Iijima broadcast throughout the world, Japan has been tripped up by North Korea.”

Japan planned to stay silent about Iijima’s trip until he got back and kept a tight lid on any information, people with knowledge of the matter said.

Only a handful of people, including Abe, Suga and Keiji Furuya, the minister in charge of the abduction issue, were involved in setting up the visit, they said.

A government source said there was no choice but to say: “I’m sorry, but I haven’t been told about it at all,” when a U.S. official asked about Iijima’s mission.