The U.N. peacekeeping mission in Western Sahara is not fully operational four months after Morocco expelled most civilian staff members to protest U.N. chief Ban Ki-moon's use of the word "occupation" to describe the status of the disputed territory, the Security Council said Tuesday.

Japan's U.N. Ambassador Koro Bessho, the current council president, said members welcomed progress in returning civilian staff and expressed "strong hope" that the mission will return to full operation as soon as possible.

But he said "there was an agreement by the (U.N.) Secretariat as well as the council members that we have not reached that goal of full functionality, and that moves are certainly needed."

Morocco annexed Western Sahara, a former Spanish colony, in 1975 and fought a local independence movement called the Polisario Front. The U.N. brokered a ceasefire in 1991 and established a peacekeeping mission to monitor it and help prepare a referendum on the territory's future, which has never taken place.

Morocco considers Western Sahara its "southern provinces" and has proposed wide-ranging autonomy, but the Polisario Front insists on self-determination through a referendum for the local population as called for in U.N. resolutions.

The secretary-general's reference to "occupation" of the vast mineral-rich territory touched off protests in Morocco and led to the expulsion of more than 70 civilian staff.

U.N. spokesman Farhan Haq said Tuesday that the U.N. and Morocco have agreed to a phased return of civilian staff, and that 25 staffers returned this month in the first phase. "We'll have to see what further returns can happen," he said.

The Security Council approved a resolution in April extending the U.N. mission, known as MINURSO, for a year and calling on Morocco to restore the mission "to full functionality." It asked the secretary-general to report within 90 days on whether the mission's operations had been restored, and if not "to consider how best to facilitate achievement of this goal."

Bessho said that at Tuesday's closed meeting, the council was briefed by U.N. peacekeeping chief Herve Ladsous and the U.N. envoy for Western Sahara. He said members took no action.

Neither Bessho nor Morocco's U.N. Ambassador Morocco's Omar Hilale would say how many civilian staff were needed to restore "full functionality."

"The problem is not the number," Hilale stressed. "The problem is the functionality. The problem is the efficiency. The problem is the mandate."

The Polisario Front wrote a letter to the council last Friday accusing the council of allowing Morocco "to persist in its attempts to intimidate and undermine the independence and credibility of MINURSO." It urged the council to consider how best to return the mission to "full functionality" and to adopt "a more urgent and proactive approach in moving forward the political process" that allows the people of Western Sahara to exercise their right to self-determination.

Bessho told reporters that at Tuesday's meeting many council members "pointed to the importance of the resumption of direct negotiations towards the political solution that will provide for the self-determination of the people of Western Sahara."