The US imposed sanctions on the former prime minister of Georgia and billionaire founder of the Georgian Dream party, Bidzina Ivanishvili.
US Secretary of State Anthony Blinken said Ivanishvili and his party had “derailed Georgia's Euro-Atlantic future”, leaving it vulnerable to Russia.
Ivanishvili is not an elected official but is described as the “honorary chairman” of Georgian Dream, which spent 12 years in power.
The party claimed victory in the last election amid allegations of fraud and quickly announced the suspension of EU accession talks, sparking widespread protests.
Opposition MPs are boycotting the new parliament, accusing themselves of fraud.
The inauguration of a new president – former Manchester City football player Mikhail Kavelashvili from the People's Power party, which is considered an ally of Georgian Dream, is scheduled for two days.
But outgoing president Salome Zurabishvili, who is strongly pro-European, has said she will not step down until new elections are held.
“We strongly condemn the actions of Georgian Dream under the leadership of Ivanishvili, including the ongoing and violent repression against Georgian citizens, protesters, members of the media, human rights activists and opposition figures,” Blinken said in a statement.
Blinken accused Georgian Dream of “continued and violent repression” against Georgian citizens, protesters, journalists, human rights activists and opposition figures” and said the party's actions had “restricted the exercise of fundamental freedoms”.
“The result has left Georgia vulnerable to Russia, which continues to occupy more than 20 percent of Georgia's territory,” he said.
US State Department spokesman Matthew Miller described Ivanishvili as the “honorary chairman” of Georgian Dream.
In November, Georgian Prime Minister Irakli Kobakhidze said his government would not seek EU accession talks until 2028, sparking ongoing protests.
Riot police used tear gas and water cannons against the protesters, who retaliated by throwing fireworks and stones.
The UK has sanctioned five other high-ranking Georgian officialsincluding the interior minister, for their role in suppressing pro-European protests.
Last month, the European Parliament backed a resolution describing the elections as the latest stage in Georgia's “deteriorating democratic crisis”.
He expressed particular concern about reports of voter intimidation, vote buying and manipulation, and harassment of observers.