Sihanouk called for a "fraternal" meeting of the four Cambodian factions.
Several important aspects of the plan have yet to be decided, and rival Cambodian factions apparently still must reach some agreement among themselves.
American officials say there will not be a political settlement until the Cambodian factions test one another on the battlefield.
Conference participants said the Cambodian factions appeared to want to fight further to test each other's military strength before they resumed negotiations.
His endorsement would be important for the peace settlement that the Cambodian factions and the major powers are hoping to reach before long.
This framework for peace must now be sold to the four Cambodian factions.
But their allies among the Cambodian factions are proving recalcitrant.
"Before we said the internal aspect must be discussed by the Cambodian factions."
On Tuesday, the Cambodian factions reached agreement to reduce their military forces by 70 percent.
The five nations said they would "welcome an early resumption of a constructive dialogue among the Cambodian factions."