Il Nuovo Postiglione - China's Xi congratulates new Japan PM Ishiba

Relations between the countries have worsened as China builds its military presence around disputed territories in the region, and as Japan boosts security ties with the United States and its allies.

Xinhua news agency said that Xi on Tuesday told Ishiba he hoped the "neighbours separated by a strip of water" could find common ground to "build a constructive and stable" relationship.

"It is in the fundamental interests of the two peoples to follow the path of peaceful coexistence, friendship for all generations, mutually beneficial cooperation and common development," Xi told Ishiba, according to Xinhua.

Japan and China have had diplomatic relations for more than 50 years, but the key trading partners have seen relations sour significantly.

Beijing last week reacted angrily and lodged a complaint with Tokyo after a Japanese warship sailed through the Taiwan Strait for the first time.

The United States and its allies are increasingly crossing through the 180-kilometre (112-mile) Taiwan Strait to reinforce its status as an international waterway, vexing China.

The destroyer Sazanami made the unprecedented passage on Wednesday, several Japanese media outlets reported.

Beijing's foreign ministry spokesman Lin Jian said China was "highly vigilant about the political intentions of Japan's actions".

The countries have also clashed recently following the stabbing of a Japanese schoolboy in the southern Chinese city of Shenzhen.

Beijing and Tokyo last year clashed after Japan began discharging treated water from the disabled Fukushima nuclear plant into the Pacific Ocean in an operation the UN atomic agency said was safe.

But the release generated a fierce backlash from China, which branded it "selfish" and banned all Japanese seafood imports.

However, China last month said it would "gradually resume" importing the seafood.

- Backs military alliance -

Ishiba, 67, says he intends to call a general election for October 27. He won a tight race on Friday to lead the Liberal Democratic Party, which has governed Japan almost continuously for decades.

The former defence minister outlined his policies at a news conference late Tuesday, warning that "the security environment surrounding our country is the most severe since the end of World War II".

"With the Japan-US alliance as a foundation, we will expand the circle of friendly and like-minded countries, using diplomacy and defence to realise the peace of Japan and the region," he said.

Ishiba, who visited Taiwan in August, backs the creation in the region of a military alliance along the lines of NATO, with its tenet of collective defence.

"Replacing Russia with China and Ukraine with Taiwan, the absence of a collective self-defence system like NATO in Asia means that wars are likely to break out because there is no obligation for mutual defence," Ishiba said in a recent policy paper.

A.Riccobono--INP