WASHINGTON (Reuters) - China has failed to send home North Korean workers by a December deadline in violation of United Nations sanctions, a senior U.S. official said on Wednesday, adding that this was why Washington blacklisted two entities involved in Pyongyang’s labor export.

FILE PHOTO: North Korean fishermen are seen as a Chinese flag flutters from the Broken Bridge as the sun sets over the Yalu River between the North Korean town of Sinuiju and Dandong in Liaoning Province, China, November 19, 2017. REUTERS/Damir Sagolj/File Photo

A 2017 U.N. Security Council resolution, which China backed, demanded that all countries repatriate all North Korean workers by Dec. 22 to stop them earning foreign currency for North Korea’s nuclear and ballistic missile programs.

The United States has estimated Pyongyang was earning more than $500 million a year from nearly 100,000 workers abroad, of which some 50,000 were in China and 30,000 in Russia.

“Many – most ... have actually taken this to heart and moved them,” a senior State Department official told reporters, referring to the repatriation requirement.

“But we know one particular country has the large majority of North Korean guest workers and has not taken action, hence the steps we had to take in terms of sanctions.”

In response to question, the official confirmed he was referring to China.

China’s embassy in Washington did not immediately respond to a request for comment.

Washington last week imposed sanctions on two North Korean entities, including China-based lodging facility Beijing Sukbakso, saying they were involved in sending North Koreans to work abroad in violation of U.N. sanctions.

Countries were required to submit a midterm report to the U.N. Security Council North Korea sanctions committee early last year on compliance with the 2017 resolution and are now due to submit a final report in late March on how many North Korean workers they have repatriated.

According to Russia’s midterm report, it sent home nearly two-thirds of some 30,000 North Koreans working there during 2018, while Beijing said it had repatriated more than half but did not specify a figure.

“China will continue earnestly implementing its international obligations, carry out the repatriation work in an orderly manner and complete the repatriation on time,” China’s U.N. mission said at the time.

The State Department official also said Washington still hoped North Korea would engage in negotiations over its nuclear program, regardless of the apparent change in its foreign minister.

Last week, North Korea told countries with embassies in Pyongyang that Ri Son Gwon, a senior military officer and official of the ruling Workers’ Party, had been appointed foreign minister.

Asked whether this was the case, the U.S. official said: “apparently, yes.”

“I don’t have a lot of data on who he is, or what he represents,” he added.

“But the hope is that they’ll understand the importance of having a conversation and talking about these things as we agreed in the original Singapore agreement,” the official said.

“There’s nothing to be gained by not talking. It’s only to their benefit.

North Korea reiterated on Tuesday it was no longer bound by commitments to halt nuclear and missile testing, blaming the United States’ failure to meet a year-end deadline for nuclear talks and “brutal and inhumane” U.S. sanctions.