The monarch said in a televised address on Monday that Morocco would not relent its claim over the territory.
His comments come amid renewed efforts by the UN to resolve the decades-old dispute.
“Past experiences should make it possible to meditate on the obvious: the problem is not so much to find a solution to this case … It is therefore up to the parties of origin of this conflict, to assume full responsibility for the search for a definitive settlement,” said Mohammed VI.
The UN Security Council adopted a resolution in April that called for a new push for talks between Morocco and the Polisario.
The King said Morocco was committed to contributing to the “new momentum” desired by the United Nations and to cooperating with the new envoy.
“We will give full respect to the principles and fundamentals adopted by the Security Council for the treatment of this artificial regional conflict. The UN body is, in fact, the only international forum responsible for overseeing the settlement process,” he added.
A national referendum was promised after a UN-brokered ceasefire in 1991, but never carried out due to wrangling over who was eligible to vote. Furthermore, international peace efforts have borne little fruit.