China's block came before a new closed-door council meeting on North Korea, also requested by Washington, and was followed by Russia's decision to similarly oppose the American proposal.

Under current UN rules, the block period lasts for six months. After that, another council member can extend the block for three more months and one day, before the proposal is permanently removed from the negotiating table.

Along with Beijing, Moscow has long held a line against increasing pressure on North Korea, even asking for relief from international sanctions for humanitarian reasons.

Last week, after Washington levied sanctions on five North Koreans linked to the country's ballistic missile program, the United States undertook a campaign within the Security Council to extend UN sanctions to those same five people.

The US Treasury Department said one of the North Koreans being sanctioned, Choe Myong Hyon, was based in Russia and had provided support to North Korea's Second Academy of Natural Sciences (SANS), which is already subject to sanctions.

Also targeted were four China-based North Korean representatives of SANS-subordinate organizations, the Treasury Department said: Sim Kwang Sok, Kim Song Hun, Kang Chol Hak, and Pyon Kwang Chol.

Washington has accused all five of ties to North Korea's weapons of mass destruction program.

North Korea has launched a series of missile tests, asserting its "legitimate right" to self-defense.

The Chinese diplomatic mission to the UN did not immediately respond to a request for comment.

- 'We have to respond' -

Thursday's meeting of the UN Security Council on North Korea, the second in eleven days, was devoted to discussing a "response to the latest tests," according to the US ambassador to the United Nations Linda Thomas-Greenfield.

"We have to respond to them. These actions are unacceptable," Thomas-Greenfield said during a virtual interview with the Carnegie Endowment for International Peace, a research institute.

North Korea hinted Thursday it could resume its nuclear and long-range ballistic missile tests, as top officials led by Kim Jong Un said the country was preparing for a "long-term confrontation" with the United States, state-run media reported.

China said Monday it had reopened its border with North Korea for freight train trade, some two years after it was shuttered by Pyongyang because of the coronavirus pandemic.