(In this July 12 story corrects paragraphs 4 and 10 to say that the U.S. listed 89 illicit transactions, not 89 North Korean tankers)

A North Korean flag flutters on top of a 160-metre tower in North Korea's propaganda village of Gijungdong, in this picture taken from the Tae Sung freedom village near the Military Demarcation Line (MDL), inside the demilitarised zone separating the two Koreas, in Paju, South Korea, April 24, 2018. REUTERS/Kim Hong-Ji

UNITED NATIONS (Reuters) - The United States accused North Korea on Thursday of breaching a U.N. sanctions cap on refined petroleum by making illicit transfers between ships at sea, according to a document seen by Reuters, and demanded an immediate end to all sales of the fuel.

The United States submitted the complaint to the U.N. Security Council North Korea sanctions committee. The charge of a sanctions breach comes as Washington engages North Korea in a bid to convince Pyongyang to give up its nuclear weapons.

The North Korea U.N. mission did not immediately respond to a request for comment on the U.S. accusation. North Korea relies on imported fuel to keep its struggling economy functioning.

The United States said that as of May 30, there had been 89 illicit ship-to-ship transfers of refined petroleum products this year.

The United States did not broadly say which countries it believed were illicitly providing North Korea with refined petroleum. But it does mention one case of a ship-to-ship transfer involving a Russian-flagged ship and one case involving a Belize-flagged ship.

Reuters in December reported that Russian tankers had supplied fuel to North Korea by transferring cargoes at sea.

The 15-member Security Council capped refined petroleum product exports to North Korea at 500,000 barrels a year in December, down from a previous limit, adopted in September, of 2 million barrels a year.

According to the Security Council North Korea sanctions committee website, only Russia and China have reported legitimate sales of some 14,000 tons of refined petroleum to North Korea in 2018.

“These sales and any other transfer must immediately stop since the United States believes the DPRK has breached the ... refined petroleum products quota for 2018,” the United States said in a document submitted to the committee, using an acronym for North Korea.

The United States provided a list to the Security Council committee of 89 illicit North Korean transactions and a few select photos, seen by Reuters.

“If fully loaded at around 90 percent laden, DPRK tankers have delivered nearly triple the 2018 quota at 1,367,628 barrels,” the United States said.

It asked the North Korea sanctions committee to issue an urgent note to all U.N. member states notifying them that North Korea has breached the refined petroleum cap and order an immediate halt to all transfers.

The U.N. Security Council has unanimously boosted sanctions on North Korea since 2006 in a bid to choke off funding for Pyongyang’s nuclear and ballistic missile programs, banning exports including coal, iron, lead, textiles and seafood, and capping imports of crude oil and refined petroleum products.

In March the council blacklisted dozens of ships and shipping companies over oil and coal smuggling by North Korea.