The tycoon is rumored to have influence in the administration while activists say he controls at least 30 parliament deputies in the president's party.
In his statement, Blinken accused Kolomoyskiy of being "involved in corrupt acts that undermined rule of law and the Ukrainian public’s faith in their government’s democratic institutions and public processes" while serving as governor. Kolomoyskiy used "his political influence and official power for his personal benefit," Blinken’s statement said.
Separately, the FBI is investigating Kolomoyskiy and business partner Hennadiy Boholyubov in connection with the $5.5 billion bailout of PrivatBank, once Ukraine's largest lender.
The tycoons are accused of embezzling billions of dollars from the bank through fraudulent loans and using some of the proceeds to buy assets in the United States, including real estate and metals plants.