A mysterious Russian satellite has raised red flags for U.S. government officials because of its “very abnormal behaviour.”

At a conference on disarmament in Geneva this week, the assistant secretary of the U.S. Bureau of Arms Control, Verification and Compliance said the orbiting satellite’s behaviour is inconsistent with “anything seen before” from similar objects. 

We don’t know for certain what it is and there is no way to verify it. But Russian intentions with respect to this satellite are unclear and are obviously a very troubling development,” Yleem D.S. Poblete said.

She noted that Russia’s space force commander has previously said that assimilating new weapon prototypes into the force was a “main task” facing the Russian troops.

Poblete told the conference that Russian officials have denied that its satellites are meant to be hostile. After the mysterious object was launched into space last October, the Russian Ministry of Defense put out a press release stating it’s simply one of its inspector satellites, she added.

“The United States has serious concerns about the activities of the Russian government in developing anti-satellite weapons, which we have shared many times in this forum,” Poblete said.

U.S. President Donald Trump and his administration have been pushing for the establishment of a U.S. Space Force as a separate military service by 2020.