BEIJING — China on Thursday ordered North Korean-owned businesses to close, cutting foreign revenue for the isolated North under U.N. sanctions imposed over its nuclear and missile programs.

China is North Korea’s main trading partner, making Beijing’s cooperation essential to the success of sanctions aimed at stopping the North’s pursuit of weapons technology. China, long North Korea’s diplomatic protector, has gone along with the latest penalties out of growing frustration with leader Kim Jong Un’s government.

North Korean businesses and ventures with Chinese partners must close within 120 days of the U.N. Security Council’s Sept. 11 approval of the latest sanctions, according to the Ministry of Commerce. That would be early January.

North Korean companies operate restaurants and other ventures in China, helping to provide the North with foreign currency. North Korean laborers work in Chinese factories and other businesses.

Also Thursday, China’s Foreign Ministry appealed for dialogue to defuse the increasingly acrimonious dispute between President Donald Trump’s government and North Korea.

“The Korean Peninsula nuclear issue is related to regional peace and stability,” ministry spokesman Lu Kang said. “Breaking the deadlock requires all relevant parties to show their sincerity.”

Chinese leaders argue against doing anything that might hurt ordinary North Koreans. They agreed to the latest sanctions after the United States toned down a proposal for a total ban on oil exports to the North.

Chinese officials complain their country bears the cost of enforcing sanctions, which have hurt businesses in its northeast that trade with the North.

The latest round of U.N. sanctions bans member countries from operating joint ventures with North Korea, most of which are in China.

They also ban sales of natural gas to North Korea and purchases of the North’s textile exports, another key revenue source. They order other nations to limit fuel supplies to the North.

Meanwhile, the United States will send “strategic” military assets to South Korea on a more regular basis to better deter North Korea, the South’s national security adviser said Thursday.

Chung Eui-young, national security adviser to President Moon Jae-in, told lawmakers in Seoul that American “strategic assets” could be deployed to South Korea on a “rotational” basis before the end of the year.

“This will help us expand our defense capabilities,” he told the lawmakers, according to Park Wan-joo, spokesman of the ruling Democratic Party.

He did not define “strategic assets,” but South Korean officials usually use the term to refer to B-52 bombers, stealth warplanes, nuclear-powered submarines and aircraft carriers.

The Pentagon confirmed that Moon and Trump agreed to “enhanced deployment of U.S. strategic assets in and around South Korea on a rotational basis.”