PHNOM PENH, Cambodia -- Cambodian opposition leader Sam Rainsy was stripped of his lawmaker status and parliamentary immunity Monday, paving the way for his arrest in connection with a defamation case that the opposition says is politically motivated.

Rainsy, who was on a visit to South Korea, announced in a Facebook post that he would not fly home Monday evening as scheduled, but that he planned to return "in the next few days." Officials from his party said he had delayed his return to avoid the possibility of violence.

"Sam Rainsy is not afraid of coming back and going to jail, but he is worried about a confrontation between his supporters and authorities," said Eng Chhay Eang, an opposition lawmaker.

The prospect of Rainsy's arrest sparked criticism and fears of unrest in the politically volatile nation, which has seen several bouts of violence following crackdowns by authorities on opposition supporters.

The U.S. Embassy in Phnom Penh called on the National Assembly to "immediately" reinstate Sam Rainsy as a lawmaker and restore his immunity.

"Today's actions are the latest incidents of harassment and intimidation of Cambodia's opposition," the embassy said in a statement, which also called on the government to revoke the warrant for Rainsy's arrest.

The Phnom Penh Municipal Court ordered the arrest of Rainsy on Friday in connection with a defamation case brought by Foreign Minister Hor Namhong in 2008. In a speech, Rainsy had accused Hor Namhong of colluding with the Khmer Rouge while being held as a prisoner by the radical group.

The court convicted Rainsy in 2013 and sentenced him to two years in jail. Rainsy appealed but lost. The conviction was never enforced and he continued to live freely in Cambodia, serving as the leader of his party in Parliament.

On Monday, amid questions about the legality of arresting a sitting lawmaker, the National Assembly's standing committee called a special session and emerged with a statement saying it had revoked Rainsy's special privileges.

"Sam Rainsy has lost his parliamentary privileges, his rights and membership as a lawmaker of the National Assembly," it said.

The 13-member standing committee comprises seven lawmakers from Hun Sen's ruling Cambodian People's Party and six from the opposition Cambodia National Rescue Party, all of whom boycotted the special session.

Rainsy's allies in the opposition party have accused Hun Sen of being behind a move to gain the upper hand in their ongoing political fight.

Rainsy has been engaged in a war of words with Hun Sen. On Thursday, the prime minister called Rainsy the "son of a traitor" after Rainsy said in Tokyo that Myanmar opposition leader Aung San Suu Kyi's election victory this month foreshadowed the downfall of Hun Sen.

While Cambodia is formally democratic, the government is notorious for intimidating opponents. Hun Sen, who has been in office for almost three decades, has warned of civil war if the opposition wins the next election, suggesting that his followers would not accept such a result.