US Secretary of Defence Lloyd Austin described Russia's Wagner Group private army as a "terrorist" organisation on Wednesday, a designation the Biden administration has so far shied away from.
"I think they are a horrible, terrorist organisation," the Pentagon chief said at a Senate hearing when asked about the mercenary group.
In January, the US formally designated the Wagner Group as a transnational criminal organisation, freezing its American assets for helping Russia's military in the Ukraine war.
But Washington has not called Wagner a terrorist group, although it is facing growing pressure from several European nations to do so, in an effort led by France.
The Wagner Group is led by Yevgeniy Prigozhin and is already the target of US sanctions. A terrorist designation would give Washington more tools to pursue Wagner.
In February, a bipartisan group of US senators re-introduced the Holding Accountable Russian Mercenaries (Harm) Act that seeks to designate Wagner as terrorists.
Mr Prigozhin's force has been accused of destabilising African nations and carrying out war crimes. In Ukraine, Wagner troops have been leading the assault in the battle for Bakhmut.
He last week threatened to pull his soldiers out of the devastated eastern city because they had no ammunition and could die needlessly, but this week he said they would stay after being promised materiel.
When asked about whether the Wagner Group should be designated a Foreign Terrorist Organisation, State Department spokesman Vedant Patel said that the group did not meet that level.
"We continue to believe that the group is largely motivated by profit, not motivated by fame or some of these other things that are made when assessments are happening for a potential FTO designation," Mr Patel said on Monday.
