By Prak Chan Thul
PHNOM PENH (Reuters) - A Cambodian court on Friday issued an arrest warrant for opposition leader Sam Rainsy in an old defamation case as tension rises between Sam Rainsy and Prime Minister Hun Sen after a political truce collapsed.
There are three years to go before a general election in Cambodia but acrimony between the two is threatening to plunge the Southeast Asian nation back into political conflict.
Former finance minister Sam Rainsy was abroad on Friday. A party colleague denounced the warrant as "politically motivated" and said it was not clear if he would return as scheduled on Nov. 16.
The warrant was issued a day after self-styled strongman Hun Sen threatened in a speech broadcast on his Facebook page to launch a lawsuit against Sam Rainsy for comments he made abroad about the election.
Sam Rainsy called on the international community to ensure that Hun Sen sticks to the election timetable and does not use the deteriorating political situation to delay the vote.
In Washington, the United States called on Cambodian authorities to drop the charges and said it was deeply concerned about the "deteriorating political climate" in the country.
"The timing of these charges gives the appearance of undue political influence in the judicial process," State Department spokesman Mark Toner said. "More broadly, the pattern of actions against the opposition suggest a return to the harsh political practices and tactics that the Cambodia people have made clear they no longer want."
Hun Sen has been in power for more than 30 years and has warned that an election victory for the opposition in 2018 would see a return to civil war.
Lawmakers from Sam Rainsy's Cambodia National Rescue Party (CNRP) were beaten outside parliament last month, and his deputy was sacked from a key parliamentary post.
The arrest warrant relates to a conviction for defamation against Sam Rainsy for which he has already received a royal pardon, government spokesman Phay Siphan told Reuters.
He was sentenced in absentia to two years in jail and fined $2,000 for defamation and incitement to provoke discrimination for remarks he made about the country's foreign minister in 2008. He received a pardon from the king in July 2013.
Sam Rainsy and his deputy, Kem Sokha, were on a trip to South Korea on Friday, CNRP lawmaker Eng Chhay Eang said.
The CNRP ended a year-long parliamentary boycott after a deal in July 2014 with Hun Sen's long-ruling Cambodian People's Party that granted a series of concessions to the opposition party.
The deal fell apart after a year, when opposition party lawmakers were jailed for insurrection for their role in a protest.
(Reporting by Prak Chan Thul; editing by Simon Webb, Robert Birsel, Grant McCool)