SEOUL, South Korea (AP) — South Korean President Lee Jae Myung said Wednesday he asked Chinese President Xi Jinping to serve as a mediator to help resolve the North Korean nuclear crisis and ease animosities between the two Koreas. He said he made the request when the two leaders met for a summit earlier this week.

Speaking with reporters traveling with him on the Shanghai leg of his China trip, Lee cited Xi as replying that patience was needed on North Korean issues during their Monday summit in Beijing.

“We’re making efforts but all our channels (with North Korea) are completely blocked so we can’t communicate at all. I told him it would be good for China to play the role of a mediator for peace,” Lee said in televised comments. “President Xi appraised our efforts and said we need to be patient.”

China is North Korea’s biggest trading partner and major diplomatic backer. South Korea and the U.S. have repeatedly asked China to use its unique influence to persuade North Korea to resume long-dormant diplomacy or denuclearize. China has urged all parties involved in North Korean issues to exercise restraint, and in recent years repeatedly blocked the U.S. and others’ attempts to toughen sanctions on North Korea despite its weapons tests banned under U.N. resolutions.

North Korea has refused to engage in dialogue with South Korea and the U.S. and has taken steps to expand its nuclear arsenal since its leader Kim Jong Un’s high-stakes nuclear diplomacy with President Donald Trump collapsed in 2019.

Since taking office last June, Lee’s liberal government has been pushing hard to reopen talks with North Korea, but Pyongyang has largely ignored Lee’s overture. In July, Kim’s sister and senior official, Kim Yo Jong, said the Lee government’s “blind trust” in South Korea’s alliance with the U.S. and hostility toward North Korea made it no different from its conservative predecessor.

Lee said Chinese Premier Li Qiang told him about the need to have patience as well during their separate meeting Tuesday.

“Roles of neighbors are necessary. We requested China to play such a role, and China said it will anyway make such efforts,” Lee said.

Lee said he told Chinese officials about his stated push to seek phased, gradual denuclearization steps by North Korea in return for giving it corresponding benefits. He said it’s important to freeze North Korea’s nuclear and missile programs first to prevent a further expansion of its nuclear arsenal and a potential proliferation of its nuclear weapons. He said China shared his view.

“Leaving the current status would be a loss for Northeast Asia and the entire world, because (North Korea’s) nuclear weapons are being produced continuously,” Lee said.

North Korea has said it won’t put denuclearization on the negotiating table again. Many experts also worry that rewarding North Korea for limited denuclearization steps could allow it to pull out of diplomacy while retaining much of its nuclear program after it wins some level of badly needed sanctions relief.