Aust fears crumbling Cambodian democracy

Australia has expressed deep concerns about a court ban on Cambodia's main opposition party.

The country's supreme court dissolved the Cambodia National Rescue Party on Thursday after it was accused of plotting to topple the government.

The party, which was poised to strongly challenge the 32-year rule of Prime Minister Hun Sen at next year's election, denies the claim.

Foreign Minister Julie Bishop said the development has serious implications for democracy in Cambodia.

"As a friend of Cambodia, Australia urges the Cambodian government to allow all its citizens to exercise their democratic rights, particularly ahead of the 2018 national election," she said in a statement.

Ms Bishop cited a series of troubling actions, including reduced access to free media, restrictions on civil society and intimidation of the opposition.

Cambodia's opposition leader Kem Sokha faces 30 years in prison after being charged with treason in September while other opposition politicians have been banned from engaging in politics for five years.

The White House has also issued a statement expressing concern about the crackdown.

"We call on the Royal Government of Cambodia to undo its recent actions," it said.

The US will terminate support for the Cambodian National Election Committee and its administration of the upcoming 2018 national election.

"On current course next year's election will not be legitimate, free, or fair," it said.