The official, speaking on condition of anonymity, said the U.S. Treasury Department will designate Wagner as a significant Transnational Criminal Organization.

"In coordination with this designation, we will also impose additional sanctions next week against Wagner and its support network across multiple continents. These actions recognize the transcontinental threat that Wagner poses, including through its ongoing pattern of serious criminal activity," the official said.

Declaring Wagner a Transnational Criminal Organization under U.S. executive order 13581 freezes any U.S. assets of Wagner and prohibits Americans from providing funds, goods, or services to the group.

"With these actions, and more to come, our message to any company that is considering providing support to Wagner is this: Wagner is a criminal organization that is committing widespread atrocities and human rights abuses, and we will work relentlessly to identify, disrupt, expose, and target those assisting Wagner," the official said.

Last month the White House said the Wagner Group took delivery of an arms shipment from North Korea to help bolster Russian forces in Ukraine, in a sign of the group's expanding role in that conflict.

North Korea's foreign ministry had called the report groundless and denounced the United States for providing lethal weapons to Ukraine. Wagner owner Yevgeny Prigozhin last month denied taking delivery of arms from North Korea and characterized the report as "gossip and speculation."

The U.S. government on Friday made public an image dated Nov. 18 that it said showed Russian rail cars traveling between Russia and North Korea.

(Reporting by Steve Holland; editing by Jonathan Oatis)

By Steve Holland