UN leader Ban Ki-moon will on Tuesday start talks with Chinese leaders in Beijing and diplomats say North Korea and Syria will top the agenda.
Ban is to meet with President Xi Xinping and other top leaders during a three day stay in Beijing, said a UN spokesman.
"He is going to be meeting the president, the premier, senior officials. He will be visiting a peacekeeping academy there," said deputy UN spokesman Eduardo del Buey.
The spokesman refused to disclose the topics that Ban would discuss.
Diplomats said however that the worsening Syria conflict and North Korea must top Ban's list in Beijing.
"Ban has taken a hard line on Syria where China has sided with Russia. But North Korea is also an urgent problem for everyone," said a UN Security Council diplomat who spoke on condition of anonymity.
China has sided with Russia three times in using a veto against Western proposed UN Security Council resolutions that would increase pressure on Syria's President Bashar al-Assad.
The UN has spoken out against China's treatment of North Korean refugees, but North Korea's nuclear program is also a major UN concern.
Ban noted North Korea's offer to hold talks with the arch-rival the United States, said del Buey.
"He has consistently stated that the parties should resolve their differences through dialogue and for any dialogue to be meaningful it should be firmly anchored in the common goal of the verifiable denuclearization of the Korean peninsula," added the spokesman.