By Tim Kelly
TOKYO (Reuters) - Differences between Japan and South Korea on how to handle North Korea emerged on Tuesday with South Korea upbeat on prospects but a more cautious Japan demanding that North Korea account for Japanese people it says North Korea abducted decades ago.
Signs of easing tension with North Korea began during the Winter Olympics last month, when the North sent a high-level delegation to the South for the Games, after more than a year of rising alarm over the North's nuclear weapon and missile tests.
Japan has been more guarded about the prospect of talks between the two Koreas, and between North Korea and the United States. Japan has warned that "talks for the sake of talks" would be unacceptable.
South Korean officials have been briefing neighbors and allies, including Japan, on a South Korean delegation's visit to North Korea last week, which included talks with leader Kim Jong Un and agreements on summits with both South Korea and the United States.
Japanese Prime Minister Shinzo Abe on Tuesday met South Korean National Intelligence Service chief Suh Hoon. Suh, a member of the South Korean team that visited North Korea, held talks on Monday with Japanese Minister of Foreign Affairs Taro Kono.
Abe told Suh that Japan wanted any denuclearization talks with North Korea to also address a dispute over the abductions of Japanese citizens by North Korean agents in the 1970s and 1980s. He also said North Korea had to show its willingness to disarm.
"A resolution of the abduction, nuclear and missile issues is Japan's core policy," Abe said.
"North Korea must match its words with actions."
A Japanese government source later said Japan was considering seeking a summit between Abe and North Korea's Kim to discuss the abductions.
Abe has made the abductions a keystone of his political career and has said he would not rest until all 13 of the people North Korea admitted to kidnapping have returned and the isolated state divulges information about the others Japan suspects were taken to train North Korean spies.
North Korea allowed five people it abducted to return to Japan.
Abe's insistence that the abductions be included in any North Korean talks may be a source of friction with South Korea.
Reflecting that possibility, South Korea's presidential office made no mention of Abe's call on the abduction issue in a statement after his talks with Suh.
The South's presidential Blue House said Abe told Suh he did not believe North Korea would use the summits to buy time to pursue its nuclear and missile programs.
A Japanese foreign ministry spokesman declined to say whether Abe had made the remark but said it was unusual for South Korea to be making statements on Japan's behalf.
Similarly, on Monday, the Blue House cited Japanese Foreign Minister Kono as saying the progress with North Korea was a "miracle".
In Japan, Kono made no mention of a miracle but said Japan and South Korea had agreed to maintain "maximum pressure" on North Korea until it takes "concrete action".
Suh was due back in Seoul on Tuesday, while South Korea's National Security Office chief, Chung Eui-yong, who led the delegation to Pyongyang, is holding talks in Russia following talks with Chinese leader Xi Jinping in Beijing on Monday.
The Chinese leader told Chung China looked forward to an important opportunity for talks.
Trump has agreed to meet North Korea's Kim by the end of May. South Korean President Moon Jae-in plans to hold his summit with Kim by the end of April.
U.S. Secretary of State Rex Tillerson, speaking on Monday in Nigeria, said preparations for Trump's meeting, including determining the location and agenda, were still at a "very early stage."
Washington had still to hear directly from Pyongyang, he added.
The White House said it fully expected the meeting to take place, if North Korea stuck to its promises.
Abe, who asked Trump for help to resolve the abduction issue in a telephone call after the planned talks were announced, said he aims to meet Trump in the United States next month.
(Additional reporting by Kiyoshi Takenaka in TOKYO, additional reporting by Christin Kim in SEOUL and Kyung Hoon Kim and Heejung Jung in TOKYO; Editing by Robert Birsel)