China has released several such lists in recent years as North Korea steps up it nuclear and missile tests. China says it is doing its duty to help enforce the increasingly tough U.N. sanctions.

The latest, extremely technical, list of dual-use goods, or products that have both civilian and military use, comes after a confidential report by independent U.N. monitors that said North Korea violated U.N. sanctions to earn nearly $200 million in 2017 from banned commodity exports.

China’s Commerce Ministry said in a statement on its website that the list was meant to comply with the requirements of new U.N. sanctions imposed last year.

The new list names dozens of banned items including air scrubbers for underwater use, equipment to simulate flying conditions for non-civilian aircraft and gas masks not for use by firefighters.

The list was jointly released with the Ministry of Industry and Information Technology, the State Administration of Science, Technology and Industry for National Defence, the China Atomic Energy Authority and the Customs Bureau.

It is effective immediately, the Commerce Ministry added.

China remains North Korea’s largest trading partner and sole major ally, though overall trade has fallen as the sanctions take effect.

Chinese analysts have regularly expressed concern that North Korea could collapse in chaos if Beijing’s policies become too harsh.

At the same time as saying it is fully committed to enforcing the sanctions, despite lingering doubts in Washington at China’s commitment, Beijing has also repeatedly called for a return to dialogue.

The announcement comes as tensions on the Korean peninsula have eased ahead of this month’s Winter Olympics in South Korea which start on Friday.

North Korea’s ceremonial leader will make an unprecedented visit to South Korea this week, officials said on Monday, as hopes grow for high-level inter-Korean talks during the Games.