A top US official Tuesday called on Cambodia to allow opposition leader-in-exile Sam Rainsy to compete in a general election this year expected to sweep the country's strongman leader back into power.
"The credibility of these elections will be judged by whether the political opposition is allowed to participate fully and fairly," said Michael Posner, US Assistant Secretary of State for Democracy, Human Rights and Labour.
"The government needs to take concrete steps to ensure a level playing field so that all political participants -- representing a wide ranges of views -- are able to compete fairly in the July elections, including Sam Rainsy," he said.
Sam Rainsy, seen as Prime Minister Hun Sen's main rival, lives in France to avoid prison for a string of convictions that critics contend are politically motivated.
The opposition leader heads the Cambodia National Rescue Party, formed last year in a merger of his Sam Rainsy Party and the Human Rights Party to challenge Hun Sen's 28-year grip on power.
Posner said July's polls will "test the government's stated commitment to promoting multiparty democracy" at a press conference during his one-day visit to Cambodia.
Sam Rainsy, 63, faces a total of 11 years in prison if he returns.
He was sentenced to 10 years in absentia in 2010 for publishing a 'false map' of the border with neighbouring Vietnam, though the punishment was later reduced to seven years.
He has two further convictions, one relating to the Vietnamese border, and the other for accusing the foreign minister of being a member of the brutal Khmer Rouge regime in the late 1970s.
In November, Cambodia's National Election Committee announced that Sam Rainsy would not be able to stand as a candidate in the elections because of the court rulings.
The government insists he will have to serve time in jail.
Hun Sen, 61, has ruled the country since 1985 and has vowed to stay in power until he is 90. His government is regularly accused of suppressing political freedoms and mistreatment of rights campaigners.
At the last parliamentary election in 2008, his ruling Cambodian People's Party won 90 of the 123 seats in the National Assembly.