The leader of Japan's New Komeito Party, the coalition partner of the Liberal Democratic Party in Japan's government, is scheduled to kick off his three-day visit to China on Tuesday, with the aim of cooling down tension between China and Japan over a stewing territorial row.

Natsuo Yamaguchi is tipped to bring a personal letter from Japanese Prime Minister Shinzo Abe to Chinese Vice President Xi Jinping. But it remains unclear which Chinese officials Yamaguchi is going to meet and whether Yamaguchi represents the Japanese government position, although he became the first member of a ruling party to visit China since Abe unveiled his new cabinet in late December.

Zhou Yongsheng, an expert on Japan issues at the China Foreign Affairs University, warned that the New Komeito Party, which historically has been friendlier to China, couldn't completely represent the position of the Abe administration, noting that the New Komeito Party only holds one ministerial position in Abe's cabinet.

An official from the Japanese embassy in Beijing on Monday declined to comment on Yamaguchi's planned visit over the phone.

In an earlier interview with Phoenix TV, Yamaguchi said that he would propose both China and Japan not send military planes to the airspace over the Diaoyu Islands and that he would explore the potential for a summit between leaders from both countries.

According to Kyodo News, Yamaguchi said he would seek "cooperation with China to peacefully solve" the territorial row based on the consensus that both China and Japan are playing important roles in maintaining stability in Asia.

"Yamaguchi's visit will surely open a window to repairing frayed China-Japan ties. But the moves Japan makes next are crucial," Zhou said.

Last year, South Korean President Lee Myung-bak rejected a letter from Japan's then-prime minister Yoshihiko Noda because Japan was protesting a visit by Lee to the disputed Dokdo island.

Hong Lei, a Chinese foreign ministry spokesman, reiterated Monday that Japan's so-called "existence on" or "control of" the sea area of the Diaoyu Islands are illegal and have been invalid from the very beginning.

A fleet of three Chinese marine surveillance ships on Monday continued patrolling the waters off the Diaoyu Islands and monitored Japanese ships, the State Oceanic Administration said.

Agencies contributed to this story