China has hit back after the US questioned whether Beijing and Moscow had elevated their "no limits" strategic partnership above global security by vetoing more UN sanctions on North Korea.
"We hope these vetoes are not a reflection of that partnership," senior US diplomat Jeffrey DeLaurentis told a meeting of the 193-member UN General Assembly in response to the vetoes in the Security Council two weeks ago.
"Their explanations for exercising the veto were insufficient, not credible and not convincing," DeLaurentis said.
"The vetoes were not deployed to serve our collective safety and security."
China and Russia declared a "no limits" partnership in February, nearly three weeks before Russia began its invasion of Ukraine.
Their vetoes - on proposed additional sanctions over North Korea's renewed ballistic missile launches - publicly split the UN Security Council for the first time since it started punishing Pyongyang in 2006.
During a right of reply in the General Assembly on Wednesday, Chinese diplomat Wu Jianjian said China categorically rejected "presumptious comments and accusations against China's voting position".
"China's vote against the US-tabled draft resolution was entirely reasonable and justified," Wu said.
"Continuing to increase the sanctions against DPRK (North Korea) would only make the likelihood of political solution even more remote."
The Russian UN mission did not immediately respond to a request for comment.
North Korea has carried out dozens of ballistic missile launches this year, including intercontinental rockets commonly known as ICBMs, after breaking a moratorium on tests that it self-imposed in 2018 after leader Kim Jong-un first met then-US president Donald Trump.
The United States has warned North Korea is preparing to conduct a seventh nuclear test, and says it will again push for UN sanctions if that test takes place.
Earlier on Wednesday in his speech to the General Assembly, China's UN Ambassador Zhang Jun blamed a "flip-flop of US policies" for a renewed escalation of tensions, pushing Washington to take action.
"There are many things that the US can do, such as easing sanctions on the DPRK in certain areas, and ending joint military exercises (with South Korea)," he said.
"The key is to take actions, not just talk about its readiness for dialogue with no preconditions."
DeLaurentis said Washington was "more than prepared to discuss easing sanctions to achieve the complete denuclearisation of the Korean Peninsula".
North Korea defended its development of ballistic missiles and nuclear weapons as protection against "direct threats" from the United States.
"The measures that the DPRK is taking for bolstering national defence capabilities are an inevitable choice to cope with the hostile threats of the US within the scope of self-defence rights," North Korea's UN Ambassador Kim Song told the General Assembly.