The United States on Tuesday imposed sanctions on two companies for exploiting North Korean overseas labor after a UN deadline to return workers who bring vital revenue to the regime.
The sanctions -- which block any US assets of the companies and criminalize any financial transactions with them -- come amid a stalemate in diplomacy as North Korea threatens to test a new weapon.
The Treasury Department imposed sanctions on the Korea Namgang Trading Corporation, a North Korean company which it said has maintained workers in Russia, Nigeria and the Middle East.
It also blacklisted Beijing Sukbakso, a Chinese company that has handled lodging and remittances for workers.
"The exportation of North Korean workers raises illicit revenue for the government of North Korea in violation of UN sanctions," Treasury Secretary Steven Mnuchin said in a statement.
Under a UN resolution unanimously approved in 2017, countries had until December 22 last year to send back all workers from North Korea.
Human rights groups have long charged that the workers live in virtually slavery-like conditions, with proceeds going to the cash-strapped regime in Pyongyang.
US officials in 2017 said that North Korea had some 100,000 overseas workers, bringing in $500 million a year.
The vast majority work in China and Russia although some have been seen around the world including in Eastern Europe, according to a study by the East-West Center.
The North Koreans are most frequently seen on construction sites, performing labor for long hours and staying in isolated housing.
The 2017 resolution came after nuclear and missile tests by North Korea, but US President Donald Trump soon afterward opened talks with North Korea, holding three landmark meetings with leader Kim Jong Un.
The regime has been pressing unsuccessfully for the United States to remove sanctions in return, with Kim saying on New Year's Day that he will no longer abide by the moratorium on nuclear and intercontinental ballistic missile tests.
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