Cambodia's long-serving leader Hun Sen has told a Chinese television station that his eldest son, Hun Manet, can become prime minister soon after Sunday's election.

It had been widely expected that the US and British-educated Hun Manet, 45, would take over from his father, who has ruled Cambodia for nearly four decades, but no timeframe had previously been given.

"In three or four weeks, Hun Manet can become the prime minister. It depends on whether Hun Manet will be able to do it or not," Hun Sen said in an interview with Phoenix TV aired on Thursday.

The self-styled strongman and former Khmer Rouge guerrilla turns 71 next month.

Cambodia holds an election on Sunday in which his ruling Cambodian People's Party (CPP) is running virtually unopposed, after its only rival of significance was disqualified.

His son, Hun Manet, is a candidate for the election, making his debut.

One of Cambodia's top generals, he attended the West Point military academy in the United States and has a doctorate in economics from the University of Bristol.

Asked about the succession, a CPP spokesperson Sok Eysan said there was "nothing more to confirm" than what Hun Sen said in the interview. (Reuters)