Administration officials detailed the effects of current financial sanctions on North Korea and outlined what is being done to get China to avoid trade with North Korean leader Kim Jong Un.

Speaking to the Senate Foreign Relations Subcommittee on East Asia in a hearing late last month, State Department Sanctions Policy Coordinator Daniel Fried said shipments of coal the North sells to the Chinese are the next target for the U.S. government.

“Sanctions applied to North Korea to date have created significant problems for the Kim regime…North Korean coal exports get $1billion…we are working to curtail this,” Fried said.

According to a 2016 report from Bloomberg News, tourists in North Korea are unable to buy anything with local currency due to international restrictions on the banking system. Instead, only dollars, yuan or euros are accepted.

In August, China – the primary trading partner of the North – imported more than 2 million tons of coal from North Korea. Imports of rare earth minerals from the North are banned under current U.N. Security Council resolutions put in place to block funding for the nation’s nuclear weapons program, but exceptions are allowed for the “people’s well-being”, according to a report from Reuters earlier this year.

Sen. Ben Cardin, D-MD., criticized the Chinese for undermining U.S. – crafted sanctions.

“It seems to me that, because of economic relations with North Korea, our work we’re doing has been compromised by the Chinese,” Cardin said.

Assistant Secretary of State for East Asian Affairs Daniel Russel said China allows this trade to occur in order to maintain stability on the Korean Peninsula.

“China has three No’s that they work to maintain,” Russel said. “No war, chaos or nuclear weapons. They do not want a crisis to occur on their border.”

Fried also said current U.S. policy towards Chinese economic relations with the North involves targeting of private companies that do business with the Kim family.

“It would be best if China itself put pressure on North Korea,” Fried said. “What we can do is work to convince individual companies to avoid dealing with the North.”

On Sep. 26, the United States Department of Justice moved to seize bank accounts controlled by Dandong Hongxiang Industrial and indicted four Chinese nationals for doing business with North Korea, according to The Guardian.

Assistant Secretary Russel said actions like these will continue even if Chinese officials complain.

“We will take protective steps even when they are unwelcomed by the Chinese,” Russel said.

Tuesday, Bloomberg News reported that the United States and China are negotiating again about how to curb Northern energy trade and obtain Chinese support for tighter restrictions.