China’s Commerce Ministry announced on Friday that it will cap oil supplies to North Korea and ban imports of steel and other manufactured goods, in accordance with tougher U.N. Security Council sanctions against North Korea’s nuclear missile program.

The new restrictions will go into effect over the weekend.

“Imports of North Korean food, machinery, and some other goods are already banned under the sanctions,” notes USA Today. China claims that no Chinese oil was exported to North Korea from Beijing in November, a fact meant to illustrate China’s willingness to get tough with its unruly client state, although some observers point out that Chinese oil suppliers might also have grown exasperated with North Korea’s failure to pay for its oil imports.

China supplies almost all of North Korea’s energy resources. The precise volume of exports in previous years is information the Chinese government is reluctant to disclose, so it is difficult to judge just how hard the new cap of 4 million barrels per year will hit the North Korean regime. Oil restrictions have long been seen as the ultimate leverage Beijing possesses over Pyongyang, a leverage China has been reluctant to use despite frequent American requests to do so.

The new Chinese restrictions were announced amid allegations that Chinese ships under foreign flags have been violating sanctions by transferring goods to North Korean vessels, including oil. President Donald Trump accused China of being caught “red-handed” undermining sanctions, an accusation the Chinese vehemently denied. Russian tankers have also been caught transferring fuel to North Korean ships.

The announcement was also made just as North Korea agreed to talks with South Korea over the upcoming Winter Olympics, a move viewed as either a diplomatic breakthrough, Pyongyang buckling under sanctions, a delaying tactic, or a plot to fragment the international coalition aligned against North Korea’s missile program, depending on the optimism level of the observer.

“We welcome the recent positive turn of events in the peninsular situation,” a spokesman for the Chinese Foreign Ministry said of the North-South Korea talks on Friday, adding hopes that “all relevant parties” will take the opportunity to bring the North Korean missile crisis “back to the correct track of peaceful settlement through dialogue and consultation.”

The Foreign Ministry also promised to “deal seriously” with sanctions violators, alluding to the report of Chinese ships trading oil to North Korea.