South Korea has been keeping a wary eye on upcoming government-level talks between North Korea and Japan amid concerns that the diplomatic re-engagement between Pyongyang and Tokyo comes without any progress in efforts to denuclearize the North, two South Korean diplomats said Monday. North Korea and Japan will reopen government-level talks in Beijing on Sunday for the first time in more than a year for discussions on a range of issues, including the North's abduction of more than a dozen Japanese citizens decades ago. The move comes as unpredictable North Korea is making a hawkish-dovish approach to the outside the world, while pushing ahead with nuclear and missile programs despite international sanctions. A senior South Korean diplomat, who spoke on the condition of anonymity, said Japan's diplomacy with North Korea might become a detriment to the strategic three-way cooperation among Seoul, Washington and Japan against threats posed by Pyongyang, describing the North's move as a "dialogue offensive."    "North Korea seems to undermine one side of the three-way security cooperation throughout a dialogue offensive," the diplomat said. "It also remains uncertain whether Japan could raise the issue of North Korea's nuclear program during the upcoming talks," the diplomat said, warning of the risk of playing into the North's negotiation tactics. Over the weekend, North Korea test-fired about 50 short-range rockets into the sea, the latest launches in recent weeks in an apparent show of force against joint military drills between Seoul and Washington. Asked about South Korea's stance on upcoming talks between North Korea and Japan, another diplomat replied, "We have no comments on the issue."    "So far, our basic principle is that talks between North Korea and Japan were limited to humanitarian issues such as returning the remains of Japanese nationals" who died in North Korea during World War II, he said. In a contrast, China voiced hope last week that North Korea, its key ally, and Japan would improve their frozen relations through the upcoming talks in Beijing. "We hope that the two sides can increase communication and consultations and improve their relations." China's foreign ministry spokesman Hong Lei told reporters. North Korea and Japan have never had diplomatic ties, and the abduction issue has long been a key stumbling block in normalizing their bilateral relations.