The diplomats said the Russians and Chinese notified the committee before Tuesday's deadline for objections.
The United States and 25 other countries accused North Korea of violating U.N. sanctions by importing far more than the annual limit of 500,000 barrels of refined petroleum products.
A U.S.-led complaint had asked the sanctions committee to rule that Pyongyang breached the cap and demand an immediate halt to deliveries. It said most of the excess petroleum products were obtained from dozens of illegal ship-to-ship transfers.
A Security Council diplomat said North Korea is believed to have obtained 3.5 million barrels of refined petroleum in 2018, seven times the limit.
This year, North Korea has already imported more than the limit and is "on pace" to obtain about the same amount as last year through illegal ship-to-ship transfers, the diplomat said, speaking on condition of anonymity because he was not authorized to speak publicly.
The complaint said the 500,000-barrel annual limit on refined petroleum products "is critical to maintaining pressure" on North Korea to achieve the denuclearization of the country.
Last July, Russia and China blocked a similar request from the U.S. to get the U.N. sanctions committee to publicly accuse North Korea of violating the annual quota. The Russians and Chinese are key suppliers of petroleum products to North Korea.
The Security Council imposed sanctions on North Korea after its first nuclear test explosion in 2006 and has made them tougher and tougher in response to further such tests and its increasingly sophisticated ballistic missile program.
Many diplomats and analysts credit the sanctions, which have sharply cut North Korea's exports and imports, with helping promote the thaw in relations between North Korea and South Korea, and the two summits between President Donald Trump and North Korean leader Kim Jong Un.
Negotiations between the U.S. and North Korea have been at a standstill since the Trump-Kim summit in Hanoi in February broke down over what the United States described as excessive North Korean demands for sanctions relief in exchange for only a partial surrender of its nuclear capabilities.
The quota on refined petroleum products was one of the tough sanctions imposed by the Security Council in December 2017 in response to North Korea's launch of a ballistic missile that Pyongyang said is capable of reaching anywhere on the U.S. mainland.
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