Trump signed an executive order Monday establishing a U.S. policy which allows “commercial exploration, recovery and use of resources in outer space.” The Encouraging International Support for the Recovery and Use of Space Resources order classifies outer space as a “legally and physically unique domain of human activity” instead of a “global commons.”

Russia’s space agency Roscosmos has denounced U.S. President Donald Trump’s order allowing commercial lunar mining and the extraction of other resources in space, appearing to liken the policy to colonialism.

Roscosmos said in a statement Tuesday that “attempts to expropriate outer space and aggressive plans to actually take over other planets” deter international cooperation in the space arena.

Sergei Savelyev, the agency’s deputy head in charge of international cooperation, appeared to compare Trump’s order to colonialism.

“There have already been examples in history when one country decided to start seizing territories in its own interests and everyone remembers how that turned out,” Savelyev said.

The Kremlin later said any colonization of space would be “unacceptable.”

Trump’s policy affirms a 2015 bill, which never became law, that encourages U.S. commercial entities to own and sell resources extracted from outer space.

Like the United States, Russia has been pursuing plans in recent years to return to the moon and potentially further into outer space.

Roscosmos outlined plans to establish a long-term base on the moon over the next two decades, while President Vladimir Putin has vowed to launch a mission to Mars “very soon.”