Ban warned in a report obtained by AFP today that staff cuts ordered by Rabat will weaken the MINURSO mission and "can be expected to be exploited by terrorist and radical elements."
"I call on the Security Council to restore and support the mandated role of MINURSO," said the report sent to the council yesterday.
"The risk of a rupture of the ceasefire and resumption of hostilities, with its attendant danger of escalation into full-scale war, will grow significantly in the event that MINURSO is forced to depart or finds itself unable to execute the mandate that the Security Council has set," he said.
The move was in response to a visit by Ban to the region during which he used the term "occupation" to refer to the status of Western Sahara, a term fiercely rejected by Rabat.
Ban's appeal to the Security Council put pressure on France, Senegal and Spain which have been in close contact with Morocco over the fate of MINURSO.
While the council has called for the mission to continue its work, it has been divided on the way forward.
In his report, Ban said the mission should stay on for a further 12 months, until April 2017.
The UN chief warned that downsizing MINURSO will have "significant implications for the stability of the region as well as the credibility of the Security Council and United Nations peacekeeping" worldwide.
Diplomats have raised concerns that concessions to Rabat will embolden other governments unhappy with a UN presence to take action.
Sahrawis have long campaigned for the right to self-determination and the Sahrawi Arab Democratic Republic is a full member of the African Union.
