Mr Hun Sen has also ramped up criticism of Western nations after in January cancelling annual military exercises with the United States.

"All foreigners should understand that the Khmer [Cambodian] story should be sorted by Khmer," he said, adding what while Cambodia needs foreign aid and business investment "I have never interfered in your international affairs."

The Prime Minister's comments were aimed at Western countries, particularly the US, which he accused of being hypocritical for its bombing of Cambodia during the Vietnam War.

"When you bombed on my country and you killed people, did you ever think about human rights?"

Mr Hun Sen said some have claimed he would not recognise the outcome of elections in which opposition parties are expected to poll strongly because of concerns about corruption, land grabs and lack of employment opportunities for the young.

"They predicted that in 2018 they could win, and if we don't hand over power to them they will crush us," he said.

"How can this happen if the troops are in my hands?"

Over three decades in power Mr Hun Sen, a former commander of the murderous Khmer Rouge, has often used force to crush his political opponents. He staged a coup in 1997 to oust his co-prime minister Prince Norodom Ranariddh in which dozens of people were killed.

Last weekend a senior government official declared that US President Donald Trump's attacks on the media were an inspiration to his country to observe limits on freedom of expression. He signalled a move against two radio outlets funded by the US government.

Mr Hun Sen has been presiding over a crackdown aimed at key opposition figures and parties in what critics say is a blow to hopes the country can move towards democratic rule.

The government passed legislation effectively banning anyone convicted of an offence from running for office, a move aimed at the main opposition party whose leaders have been systematically targeted in criminal prosecutions, mostly in defamation cases for comments on Facebook.

Sun Samnang, an official in Cambodia's Ministry of Defence, told the ABC commune elections in June, national elections scheduled for 2018 and budget restraints caused the Dawn Kouprey exercises with Australia to be cancelled.

Only two months ago Cambodia held if first major military exercise with China, which has become one of the country's biggest aid donors.

Australia will send $90 a million in aid to Cambodia this year, in addition to the $55 million it paid for the country to accept a handful of refugees from Nauru. That agreement has been widely criticised by the UN refugee agency, human rights and refugee groups.

Cambodian soldiers are expected to take part in a separate counter-terrorism event in Australia in 2018.