China's top-ranked diplomat intensified pressure on Japan over a territorial rift, warning Tokyo on Sunday against making "misjudgements" over the seizure of a Chinese fishing boat in disputed seas, according to Reuters. China's latest demand marked another diplomatic escalation in the territorial rift between Asia's two biggest economies and has set back efforts to ease decades of distrust. State Councillor Dai Bingguo made the warning to Japan's ambassador in Beijing, Uichiro Niwa, summoned in the early hours to hear China's call for the release of a Chinese captain and crew whose fishing boat collided with two Japanese coast guard ships in disputed seas last week, Xinhua news agency reported. Dai advises China's top leaders on foreign policy and serves on the State Council, or government cabinet, outranking the Foreign Minister within the ruling Communist Party hierarchy. "(He) solemnly stated the Chinese government's major concerns and urged Japan not to misjudge the circumstances and to make the wise political choice of immediately returning the Chinese fishermen and their boat," Xinhua reported. Japan's ambassador, Niwa, gave no indication his government was preparing to back down. "We have maintained the position that we will solemnly handle the case in strict accordance with domestic law", the ambassador said, according to Japan's Kyodo news agency, citing the Japanese embassy in Beijing. China should act "calmly and carefully" to avoid damaging overall bilateral ties, Niwa said.