A Japanese rights activist has written to every Israeli lawmaker to urge Prime Minister Benjamin Netanyahu to raise the issue of Iranian nuclear scientists entering North Korea via China when he arrives in Beijing on Monday.
Netanyahu is making the first state visit to China by an Israeli leader since 2007, with improving bilateral ties and the Syrian crisis expected to dominate the agenda.
Ken Kato, director of the Tokyo-based Human Rights in Asia, wants Netanyahu to pressure Beijing to take additional measures "to prevent the North's nuclear and missile technology from falling into the hands of Iran, Syria, Hezbollah and Hamas," he told The South China Morning Post.
"This will be a great opportunity to stop China from acting as a hub for North Korea's proliferation activities," he said.
Analysts do not believe that Pyongyang's nuclear missiles pose a major threat to global stability, primarily because its scientists still lack the ability to miniaturise a warhead for attachment to a long-range missile.
They say the more immediate threat is North Korea's willingness to sell weapons of mass destruction to other pariah regimes and, potentially, to terrorist groups.
Even after Israeli aircraft destroyed a nuclear reactor in Syria in Operation Orchard in 2007 - a facility that was built with North Korean technology - Pyongyang has continued to sell weapons to Bashar al-Assad.
"Necessary steps must be taken one by one, and I believe Israel and the international community should force China to prevent nuclear scientists and technology [from] transiting their airports," Kato's letter to Israeli lawmakers said.
He noted that Mohsen Fakhrizadeh, Iran's leading nuclear scientist, was present in North Korea when the regime conducted its third underground nuclear test on February 11.
Fakhrizadeh arrived in Pyongyang after travelling through China, Kato said.
Kato said sources told him that North Korea's airline, Air Koryo, was used to transport nuclear technology out of the country. "If Iranian scientists cannot transit through China and Air Koryo is refused from entering Chinese airspace, it would be a significant blow to North Korea's proliferation activities," Kato added.