The Biden administration has confronted China’s government with evidence that suggests some Chinese state-owned companies may be providing assistance for Russia’s war effort in Ukraine, as it tries to ascertain if Beijing is aware of those activities, according to people familiar with the matter.

The people, who asked not to be identified discussing private deliberations, declined to detail the support except to say that it consists of nonlethal military and economic assistance that stops short of wholesale evasion of the sanctions regime the U.S. and its allies imposed after Russian forces invaded Ukraine.

The trend is worrying enough that U.S. officials have raised the matter with their Chinese counterparts and warned about the implications of supplying material support for the war, the people said, though they declined to provide details of those contacts. President Xi Jinping has avoided criticizing Russia over the war but has also offered to play a role in peace talks and come out against the use of nuclear weapons in the conflict.