PHNOM PENH (Reuters) - Cambodia’s parliament stripped the main opposition leader of a key role on Tuesday, further weakening veteran Prime Minister Hun Sen’s opponents ahead of elections.

Kem Sokha (L), leader of the Cambodia National Rescue Party (CNRP), arrives before a plenary session at the National Assembly of Cambodia, in central Phnom Penh, December 7, 2016. REUTERS/Samrang Pring/Files

Kem Sokha, deputy leader of the Cambodia National Rescue Party (CNRP), had held the minority leader status under a 2014 agreement to end political deadlock and promote dialogue between Hun Sen and the Southeast Asian country’s opposition.

The ruling Cambodian People’s Party (CPP) has a slim majority in parliament and voted unanimously on Tuesday to remove Kem Sokha’s minority leader status.

The role in theory gave him the same status as the prime minister in regular talks designed to preserve political stability. The CNRP boycotted the vote.

Political tension has been rising in Cambodia, where local elections in June and a general election next year threaten Hun Sen’s three-decade grip on power.

The opposition party complained that removing Kem Sokha’s status as minority leader meant a shift in the balance of power.

After the vote, opposition CNRP lawmaker Son Chhay called for a return to negotiations.

The vote was a setback for the opposition and puts the political dialogue on “life support”, said Ear Sophal, an associate professor of diplomacy and world affairs at Occidental College in Los Angeles.

Cambodia’s rivals agreed to the regular political dialogue after a disputed election led to protests, arrests and political deadlock.

CNRP party leader Sam Rainsy lives in exile in France to avoid jail on a series of defamation convictions, and Hun Sen brought another defamation case against him this month, demanding $1 million in damages.

Rainsy says all the charges against him have been politically motivated.