A former soccer star and conservative critic of the West was sworn in on Sunday as the new president of Georgia, a strategically important republic in the middle of the Caucasus, replacing a head of state who vowed to continue fighting to steer the country closer to Europe.

Mikheil Kavelashvili, 53, was sworn in as president in a hall of Parliament that had many empty seats as representatives from four opposition parties refused to enter it after an election in October that they denounced as rigged.

The parliamentary elections and the inauguration of a conservative president known for his criticisms of Western governments represented a watershed moment for Georgia. Traditionally regarded as a pro-Western trailblazer among states that emerged after the Soviet collapse, Georgia, a country of 3.6 million people, is now widely seen as moving closer to Russia and China.

During his inauguration, Mr. Kavelashvili said that now Georgians “must approach existing challenges with caution, analyze the threats” and “make decisions not based on emotions but as a result of careful thought.”

The standoff between Georgia and its former Western backers deepened on Friday when the United States announced that it was imposing sanctions on Bidzina Ivanishvili, a reclusive oligarch and founder of the Georgian Dream party, who is widely seen as Georgia’s shadow leader.

Mr. Kavelashvili’s inauguration took place amid a political crisis in Georgia triggered by the parliamentary election, which the opposition and some European officials regard as fraudulent. The already tense crisis deepened at the end of November when Georgia’s prime minister announced that the country would suspend until 2028 talks to join the European Union, a popular national goal for Georgians.