Tokyo signals renewed interest in negotiations with a personal letter from Prime Minister Shigeru Ishiba to Chinese President Xi Jinping.

Japan had long maintained deep economic ties with both China and the United States. Recent trade tensions may challenge that approach.

"China firmly opposes any party reaching a deal at the expense of China's interests. If this happens, China will never accept it and will resolutely take countermeasures". The remarks echoed an editorial last week in the state-controlled China Daily, which warned the European Union against trying to "appease" the US.