North Korea has informed Japan that it will postpone its report on the investigation into Japanese abductees that it launched a year ago, the government said Friday.
"We are sincerely conducting a comprehensive investigation, but it will take a little more time," the government quoted Pyongyang as saying.
The Japanese government criticised North Korea for the delay.
Prime Minister Shinzo Abe instructed Foreign Minister Fumio Kishida and Eriko Yamatani, minister in charge of the abduction issue, to step up efforts to urge Pyongyang to promptly report the results of its investigation.
Kishida, Yamatani and Chief Cabinet Secretary Yoshihide Suga announced North Korea's notice of the postponement at a press conference and elsewhere on Friday morning.
Pyongyang informed Japan of the delay via diplomatic channels in Beijing on Thursday night.
Last July 4, North Korea purportedly set up the Special Investigation Committee and launched an investigation into all Japanese nationals in North Korea, including Japanese abductees, missing Japanese nationals and Japanese spouses.
Pyongyang also said it would investigate the remains and graves of Japanese nationals who died in North Korea around the end of World War II, and end the overall probe in about a year.
"It is extremely regrettable that the return of abduction victims to Japan has not been realised, even one year after the investigation started," Abe said Friday morning at a meeting of the House of Representatives Special Committee on the Legislation for Peace and Security of Japan and the International Community.
"We will step up efforts to urge North Korea to take concrete action immediately."
Abe said he has given relevant instructions to Kishida and Yamatani.
"We'll stick to the principles of 'dialogue and pressure' and 'action for action' and do all we can to realise the return of all abductees," the prime minister said.
The government is expected to call on North Korea via diplomatic channels in Beijing to describe the progress in its investigation.
It also plans to discuss the resumption of official inter-governmental talks between Japanese and North Korean officials, which have been suspended since October.
Meanwhile, the government may consider heightening its unilateral sanctions against North Korea.
Abe implied the government may strengthen sanctions if there is no progress in Pyongyang's response, saying the government will decide what to do after closely watching its actions.
The government is expected to discuss strengthening sanctions against North Korea after this month, which the government considers to be a de facto deadline for Pyongyang to report the results of its investigation.
Based on an agreement with North Korea last May, the government has lifted part of its unilateral sanctions, such as travel regulations, in return for Pyongyang's start of its investigation into the Japanese abductees.
N Korea's commitment unclear
The agreement reached between Japan and North Korea last May was narrowly saved because Pyongyang told Japan it was continuing its investigations into Japanese abductees and other matters.
However, North Korea has postponed its report on the investigation many times.
The government initially expected Pyongyang to report its findings from the end of summer to early autumn last year or by the end of 2014, but this was postponed to a year after the start of the investigation.
It is now unclear whether North Korea is seriously conducting the investigation on the Japanese abductees and others.
The government is in a difficult situation - the Liberal Democratic Party and families of abductees have only grown more frustrated, saying there is no chance of success even if Japan continues dialogue with North Korea.
However, many government officials are reluctant to toughen sanctions, saying that could send the Japan-North Korea agreement back to square one.
Calls will likely grow within the government to hold the first official inter-governmental talks since October to confirm the progress in North Korea's investigation and clearly tell Pyongyang that further delay in submitting the report on its investigation will be unacceptable to Japan.