Citing a new assessment by U.S. intelligence, she stated that the attack could occur "in the coming days."
She added that while the United States does not believe this missile will "change the game on the battlefield," Russia is attempting to use any weapon available in its arsenal "to intimidate Ukraine."
The Pentagon did not provide additional details, including potential target locations in Ukraine.
During the briefing, Singh mentioned that Russian dictator Vladimir Putin has publicly declared that Russia intends to launch another Oreshnik missile.
"It is possible that Russia might conduct a launch in the coming days; I cannot specify an exact date," AP quoted Singh.
On Dec. 10, Putin claimed that the Oreshnik IRBM "minimizes the need to use nuclear weapons."
On Nov. 21, Russia attacked Dnipro with Oreshnik, although it carried no explosive payload, resulting in minimal damage to the city.