Some analysts in the United States have called for new policies that exert pressure on a wider array of Chinese companies. Larger Chinese state-run banks and companies should be included because they are all ultimately controlled by the government, said Daniel Blumenthal, an analyst at the conservative American Enterprise Institute.

“The point would be for the Chinese Communist Party itself to feel the pain of its relationship with Kim,” said Mr. Blumenthal, referring to the North’s leader.

While obscure textile factories and border trading companies make up much of China’s trade with North Korea, a number of China’s largest brands have also occasionally shipped goods to the North in recent years, though the sales are quite small compared with those elsewhere. Some of the same companies also sell products in the United States.

Just about every prominent Chinese appliance maker has sold goods in North Korea, including TCL and Hisense. The two companies sold a range of products, including refrigerators, air-conditioner units and television screens and other electronics.

Midea, a company that took over the German robot maker Kuka last year despite some objections in Europe, has done sporadic business with North Korea. Most recently, in November, it shipped refrigeration units, air-conditioners, copper piping and other electronics.

Among China’s car companies, Great Wall, Chery and Geely have all shipped auto parts or vehicles to North Korea. During a parade this spring in honor of the birthday of Kim Il-sung, the country’s founder, a visiting journalist took photographs of trucks made by a company called Sinotruk tugging submarine missiles. The company has shipped $1.2 million in vehicles and parts to North Korea in the past several years.

The Chinese battery and electric carmaker BYD has done about $14 million in trade with North Korea since 2012 and the shipments have continued until recently. In January, the company sent rubber products to the country, and in December, it sent vehicles. BYD is traded on Hong Kong’s stock exchange, and is backed by Warren Buffett, who owns a 10 percent stake in the company.