Li also said China wanted to work with Japan to safeguard the political foundation of their bilateral relationship, deepen cooperation for mutual benefit, properly handle differences and promote the development of ties in the spirit of “taking the past as a mirror and looking forward to the future”, according to the official news agency.

Highlighting Li’s visit to Japan in May – his first since becoming premier in 2013 – Japanese Prime Minister Shinzo Abe said in his message he was “very pleased to have Japan-China relations return to a normal path”, Kyodo news agency reported. He added that both Japan and China had important duties for regional and world peace and prosperity.

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Both Li and Abe also said they were looking forward to a meeting to be held in China by the end of the year, although a date has yet to be set. When he met Li in Tokyo in May, Abe said he wanted to visit China and invited Chinese President Xi Jinping to Japan.

Japanese Foreign Minister Taro Kono and his Chinese counterpart Wang Yi also exchanged similar messages to mark the occasion.

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The Asian neighbours have been mired in a territorial row over the East China Sea, especially the uninhabited Diaoyu Islands, which are known as the Senkakus in Japan. Tensions escalated after Tokyo brought the islets under state control in 2012, but relations began improving last year.

“Sino-Japanese relations have been warming since last year – since Chinese and Japanese leaders met in Hamburg, Germany for talks in August,” said Lu Yaodong, a Japanese affairs expert with the Chinese Academy of Social Sciences.

“Abe actually said in a speech to parliament in 2017 [he] would change Japan’s relationship with China,” Lu added. “Furthermore, Japan goes to the polls this year, and its ruling Liberal Democratic Party wants to improve relations with China.”

Alexander Huang Chieh-cheng, an international relations expert with the Institute of International Affairs and Strategic Studies at Taiwan’s Tamkang University, said as relations between Beijing and Washington rapidly changed amid a trade war, Japan appeared to be shifting its approach to China.

“Japan does not want to be forced to take sides in the dispute between the United States and China, so it has to somehow adjust its relations with Beijing,” Huang said.

Zhou Yongsheng, a Sino-Japanese relations expert from China Foreign Affairs University, said while Beijing was under huge pressure from Washington on trade, the US had also engaged in disputes with Japan and other countries over steel, aluminium and cars.

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He said Tokyo would not join forces with Beijing to oppose US President Donald Trump’s trade policies, but they could work together on regional economic cooperation and pacts.

“Japan’s push for a regional free-trade agreement and economic cooperation is in effect a way to counter the US trade policies, and in this regard China and Japan could have … common ground,” Zhou said.

“Beijing should not expect Tokyo to join it and oppose Washington on trade … but they can push for economic cooperation in East Asia and an early deal on the Regional Comprehensive Economic Partnership,” he said, referring to the proposed free-trade pact among Asean members, China, Japan, South Korea, India, Australia and New Zealand.