In response to Pyongyang’s implied threat to halt bilateral negotiations, Tokyo will strongly urge the reclusive country to proceed on the promised re-investigation into the whereabouts of the Japanese nationals it abducted, Japanese sources said.

Pyongyang protested through diplomatic channels the police raid on the home of the head of the General Association of Korean Residents in Japan (Chongryon) late last month and said the negotiations “are facing difficulties.”

Japan plans to use diplomatic channels to express its intolerance of the North’s stance. It may also step up economic sanctions against the country, the sources said.

But as there is little hope Pyongyang would heed such actions, Prime Minister Shinzo Abe, who has pledged to do his utmost to secure the return of all of the Japanese abductees, is expected to be put in a bind once the negotiations stall.

Pyongyang communicated its message through an embassy-related route in Beijing, Foreign Minister Fumio Kishida told reporters Thursday night. Noting Japan and the North agreed last May on the latter’s re-investigation into the abductions, Kishida said, “We’ll strongly call on North Korea to conduct the investigation and report the results swiftly and honestly.”

A government official said the North wants to pressure Japan ahead of Abe’s meeting with relatives of the abductees.

“But this wasn’t unexpected,” the official said. “We’re going to closely watch what their next move will be.”

“We may step up anctions (on North Korea) if they don’t change their attitude,” the official added.

But chances are clearly growing slim that the two nations will be able to reconcile their differences, because the North is demanding an explanation about the raid and an apology, while Tokyo views the police investigation and the bilateral negotiations as “separate issues,” the government source said.

A senior Foreign Ministry official in Tokyo described the situation as a “stalemate.”

“Japan can only continue to make its demand. It’s a very difficult situation,” the official said.

As more severe sanctions may lead to a cancellation of the re-investigation, the government will call on the North to stick with the May agreement that confirmed the adoption of the “action rewarded with action” principle, through multiple channels, the official said.