China, Cambodia's most important diplomatic and economic backer, has endorsed a vote heavily criticized by rights groups and several Western countries as neither free nor fair.
Records show the army chief's wife held shares in a Cayman Islands company set up to own her Cambodian coal mine. The army chief is now running for public office.
The countries called on Cambodia to reinstate the main opposition party, release its jailed leader and ensure a July general election is free and fair.
The move is apparently aimed at consolidating his power ahead of an election this year.