The Japanese and South Korean leaders raised sensitive topics like Taiwan, North Korea and the South China Sea as well as ways to boost cooperation when they individually met China’s premier Sunday on the eve of a fuller trilateral meeting, according to AP.

It was unclear how serious discussions the three leaders had on those thorny issues, which are not among the official agenda items for Monday’s three-way gathering in Seoul, the first of its kind in more than four years.

No major announcement is expected from the meeting, but observers say that just resuming the highest-level talks among the three Northeast Asian neighbors is a good sign and suggests they are intent on improving relations. Their trilateral meeting was supposed to happen annually but it had stalled since the last one in December 2019 because of the COVID-19 pandemic and complex ties among the three countries.

After meeting Chinese Premier Li Qiang, Japanese Prime Minister Fumio Kishida told reporters that he expressed serious concerns about the situations in the South China Sea, Hong Kong and China’s northwestern Xinjiang region. He said Japan is closely monitoring developments on self-governed Taiwan.

He referred to China’s military assertiveness in the South China Sea, clampdowns of pro-democracy movements in Hong Kong and human rights abuses against minorities in Xinjiang. Last week, China also launched a large military exercise around Taiwan to show its anger over the inauguration of the island’s new president who refuses to accept its insistence that Taiwan is part of China.

During a separate meeting with Li, South Korean President Yoon Suk Yeol, on his part, asked China, as a permanent member of the U.N. Security Council, to contribute to promoting peace on the Korean Peninsula, while speaking about North Korea’s nuclear program and its deepening military ties with Russia, according to Yoon’s office.

Yoon’s office said Yoon and Kishida in their separate meeting expressed worries about North Korea’s nuclear program and agreed to strengthen their cooperation with the United States.

South Korea, Japan and the U.S. have long urged China — North Korea’s major ally and economic pipeline — to use its leverage to persuade the North to abandon its nuclear ambitions. But China is suspected of avoiding fully enforcing U.N. sanctions on North Korea and sending clandestine aid shipments to help its impoverished neighbor stay afloat.

The three leaders also discussed how to bolster economic and other cooperation.