The United States added to calls by Cambodia's opposition for an investigation into reports of election irregularities a day after Prime Minister Hun Sen's party declared victory to extend his 28-year rule.
"We call for a transparent and full investigation of all credible reports of irregularities,'' US State Department spokeswoman Jen Psaki told reporters in Washington on Monday.
She declined to specifically support opposition leader Sam Rainsy's demand for an investigative committee, saying it was not about supporting one call.
The ruling Cambodian People's Party claimed victory in the July 28 election with 55% of seats in the 123-member parliament, a drop from 73% before the vote. Sam Rainsy rejected the results and called for an investigation that would include members of the United Nations and foreign countries.
The outcome increases political uncertainty in one of Asia's poorest countries, where stability over the past decade has attracted companies such as General Electric, Sumitomo and DuPont. Sam Rainsy, who was barred from standing in the election, ended a four-year exile on July 19 after receiving a royal pardon for charges he says were politically motivated.
Ms Psaki cited systemic flaws in Cambodia's electoral process, including problems in the voter registry and unequal access to media. The National Election Committee has yet to release official results.
"Cambodia's government would support an investigation that is done through proper channels based on national law,'' spokesman Phay Siphan said by phone on Tuesday. He questioned the legality of the committee proposed by Sam Rainsy.
"They are rejecting the results because the opposition party doesn't get a majority in the National Assembly and saying democracy won't prevail unless the opposition party becomes the ruling party,'' he said. "Is that fair for Cambodia?''
Transparency International Cambodia, which sent observers to polling stations, said that some voters could not find names on registry lists and others were allowed to cast a ballot without proper identification. It also questioned the high number of voters who used temporary identification papers.
"TIC is very concerned about the disenfranchisement of citizens and suspect voting, which are consistent with the warnings outlined by independent organisations for the past several months,'' it said in a statement. "It also called for an independent body to investigate election irregularities.''
The CPP won 48.5% of total votes, compared with 44.4% for the opposition, according to estimates by Transparency International Cambodia.