The Trump administration has imposed sanctions on a Chinese bank, a Chinese company and two Chinese citizens in an effort to crack down on North Korea’s financing and development of weapons of mass destruction.

The sanctions follow the death of Otto F. Warmbier, an American student who was imprisoned by North Korea, and come as frustration grows in the United States government over the North’s missile tests.

The most significant action is directed at the Bank of Dandong, a Chinese lender that Treasury officials say acts as a conduit for illicit North Korean financial activity and money laundering. The department’s Financial Crimes Enforcement Network is moving to sever the bank from the American financial system, which would severely limit its ability to work with other banks around the world.

The Department of the Treasury is committed to protecting the U.S. financial system from North Korean abuse and maximizing pressure on the government of North Korea until it abandons its nuclear and ballistic missile programs.

Sanctions are also being imposed on Dalian Global Unity Shipping and two Chinese citizens who the Treasury said have business dealings with North Korea related to illicit financial transactions.

President Trump encouraged China, one of North Korea’s only allies and a major trading partner, to pressure the North to curb its nuclear ambitions.

Last week, Mr. Trump expressed his frustration on Twitter: “While I greatly appreciate the efforts of President Xi & China to help with North Korea, it has not worked out.”