More than 40 countries accused North Korea on Friday of illicitly breaching a U.N. cap on refined petroleum imports and called for an immediate halt to deliveries until the end of the year, according to a complaint seen by Reuters.

The 15-member U.N. Security Council imposed an annual cap of 500,000 barrels in December 2017 in a bid to cut off fuel for North Korea's nuclear weapons and ballistic missile programs.

But in a complaint to the U.N. Security Council North Korea sanctions committee, 43 countries – including the U.S., U.K. and France - said they estimated that in the first five months of this year Pyongyang had imported more than 1.6 million barrels of refined petroleum via 56 illicit tanker deliveries.

The complaint said North Korean vessels continue to conduct ship-to-ship transfers at sea "on a regular basis as the DPRK's primary means of importing refined petroleum." North Korea's formal name is the Democratic People's Republic of Korea (DPRK).

The countries asked the Security Council sanctions committee to make an official determination that North Korea had exceeded the cap and "inform member states that they must immediately cease selling, supplying, or transferring refined petroleum products to the DPRK for the remainder of the year."

Similar requests to the committee in 2018 and 2019 were blocked by North Korean allies Russia and China. They are also the only two countries to have formally reported deliveries of refined petroleum to the Security Council sanctions committee.

"China and Russia collectively have reported 106,094.17 barrels of refined petroleum product transfers ... January through May," the complaint said. "The official accounting of the DPRK's imports vastly underrepresents the volume of refined petroleum products that actually enter the DPRK."

The 43 countries also urged the committee to call on states to "immediately exercise enhanced vigilance regarding the DPRK attempting to procure additional refined petroleum products and to prevent illicit ship-to-ship transfers of refined petroleum products to vessels owned, controlled, or acting on behalf of or working in cooperation with the DPRK."

North Korea has been subjected to U.N. sanctions since 2006 over its nuclear and ballistic missile programs. While the Security Council has steadily strengthened sanctions, U.N. monitors reported this year that North Korea continued to enhance its programs last year.

North Korean leader Kim Jong Un and U.S. President Donald Trump have met three times since 2018, but failed to make progress on U.S. calls for Pyongyang to give up its nuclear weapons and North Korea's demands for an end to sanctions.

The complaint to the Security Council committee said: "If the DPRK is able to flagrantly evade international sanctions, it will have little incentive to engage in serious negotiations."

The North Korean mission to the United Nations in New York did not immediately respond to a request for comment.