Japan's outgoing ambassador to China, Uichiro Niwa, helped improve economic ties between the two countries but his lack of political skills in handling the territorial dispute in the East China Sea cost him his job, mainland analysts said. Niwa, who left China yesterday after two years as ambassador, will be replaced next month by Japan's assistant chief cabinet secretary, Masato Kitera. Niwa was appointed in 2010 when Sino-Japanese ties were strained by the arrest of a Chinese trawler captain in waters near the Diaoyu Islands, known as the Senkakus in Japan. The dispute flared again in April when Tokyo governor Shintaro Ishihara announced a plan to buy some of the islands. Niwa found himself at the centre of controversy in June after he said the Tokyo municipal government's plan to buy the islands could spark an "extremely grave crisis" between the two Asian powers. He was criticised by political parties in Japan. Zhou Yongsheng, an expert in Japanese affairs at China Foreign Affairs University, said Niwa's direct expression of his views offended Japanese conservatives. "This open style is not very suitable for a diplomat." Professor Yang Bojiang, from the China Institutes of Contemporary International Relations, said: "Niwa focused on the economic aspect. But he did not handle well the sentiments of the Japanese conservative camp, which constantly stir things up in relation to security and political matters." Professor Da Zhigang, of the Heilongjiang Academy of Social Sciences, said Niwa was formerly the boss of a trading company in Japan. "What he said may represent the views of the Japanese business sector, but not the government," Da said. Analysts said Niwa's successor, Kitera, would face a tricky situation, with Japan's ruling Democratic Party likely to lose next month's election, paving the way for the Liberal Democratic Party, under conservative former prime minister Shinzo Abe, to return to power.