HONG KONG — The Cambodian government on Friday sued to dissolve the country’s main opposition party, intensifying a crackdown that has drawn widespread condemnation from Western governments.

The action comes just weeks after the government formally charged Kem Sokha, the leader of the Cambodia National Rescue Party, with treason, accusing him of plotting to overthrow government leaders with the backing of the United States. If convicted, Mr. Kem Sokha could be jailed for up to 30 years.

In moving to dissolve the opposition, government lawyers said the party conspired with foreigners to topple the government, Reuters reported. The lawyers cited as evidence a 2013 video clip that it says showed Mr. Kem Sokha discussing a plan to gain power with American help.

Prime Minister Hun Sen, who has been in power for 32 years, is preparing for parliamentary elections next year. In 2013, Mr. Kem Sokha’s party stunned the government by nearly winning parliamentary elections, drawing support from young people seeking greater political and social freedom.