PHNOM PENH: Cambodian Prime Minister Hun Sen vowed to extend his more than 30 years in power by at least another decade on Wednesday, weeks after the highest court dissolved the main opposition party ahead of a 2018 general election.

The Cambodia National Rescue Party (CNRP) was dissolved in November at the request of Hun Sen's government, signalling what one rights group called the "death knell" for democracy in the Southeast Asian country.

Hun Sen, a former Khmer Rouge cadre who defected from the genocidal group and helped drive it from power in 1979, is credited with helping Cambodia achieve economic growth but has also been criticized for his crackdown on civil society groups and the media.

China, Cambodia's biggest backer, has said it supports the government's attempts to maintain Cambodia's national security.

At a speech given to thousands of garment workers on Wednesday at a pagoda on the outskirts of Phnom Penh, Hun Sen said he would stay in power for another two terms and asked workers to vote for his Cambodian People's Party (CPP).

"I will continue to be the elected Prime Minister for another two mandates which is not less than 10 years," Hun Sen said.

"I hope that you as well as your parents and grandparents, if they are alive, and your families continue to vote, to support CPP on July 29, 2018."

Garments are Cambodia's biggest export by far and garment workers are a politically powerful group. In 2016, garment exports were worth $6.3 billion and reached $4.9 billion in the first seven months of 2017.

Hun Sen has been courting garment workers ahead of the vote. He has promised money for female workers who give birth, among other things.

"You have to remember that if you want to keep jobs ... you should not give opportunity to anyone, including Cambodians and foreigners, to destroy peace," Hun Sen said.

Concerns about the impact of next year's election and competition from lower-cost Asian rivals will slow the growth of Cambodia's garment industry next year, the main manufacturers' group said earlier this month.