The U.S. has called on China to exert its influence on North Korea amid reports that a sanctioned North Korean oil tanker was spotted near Chinese waters.

In a press briefing on Wednesday, State Department deputy spokesperson Vedant Patel said Washington believes “Beijing can have a constructive role to play in reining in some of the North’s destabilizing activities.”

He made the remark after being asked to comment on such reports while quickly noting that he is not aware of the details, saying only that attempts to subvert sanctions by a North Korean vessel subject to such restrictions would be “concerning.”

The comments came after the Voice of America said earlier in the day that ship-tracking website MarineTraffic had spotted a North Korean oil tanker, the Mu Bong 1, in waters east of the Chinese Port of Ningbo-Zhoushan on Monday. The tanker reportedly has a history of violating UN sanctions.

On Pyongyang’s claims that it is boosting its weapons-related activities due to hostility from the U.S., Patel emphasized that Washington is “not, in any way, harboring any hostilities” towards the North.

He went on to say that discussions on the ultimate goal of the denuclearization of the Korean Peninsula include the U.S.’ clear willingness to engage with North Korea without preconditions, and that stance will remain in place.