The United States said Saturday it was "deeply concerned" by reports that opposition lawmakers have been expelled from Cambodia's national assembly.
"Such a decision starkly contradicts the spirit of a healthy democratic process," State Department spokesperson Jen Psaki said.
On Wednesday, the 28 lawmakers belonging to Cambodia's two only opposition parties were told they were no longer valid members of parliament by a permanent parliamentary committee made up of ruling party members.
The committee said it was taking the step as the parties had joined to form a new opposition organization ahead of July elections and were therefore not eligible to remain as MPs.
Opposition lawmakers rejected the move and said parliament itself was rendered invalid by telling them they were no longer MPs.
Parliament is currently not in session as it takes a break before the July 28 polls.
Saying the United States was "deeply concerned" by the reports, Psaki called on assembly leaders "to allow all elected members to fulfill their commitment to serve the Cambodian people."
"We strongly support a political process that includes the full participation of all political parties on a level playing field," she said in a statement.
"Stripping the salaries and parliamentary status of opposition party legislators deprives the Cambodian people of their voice and hurts the democratic process in Cambodia.
"Full participation of all elected representatives is essential to the democratic process," Psaki added.