The decision on the area, contested between Morocco and the separatist movement the Polisario Front, was taken on Friday.
The 15-member body adopted a resolution, sponsored by Britain, Spain, Russia and the United States, that calls on the parties and states in northwest Africa "to continue to cooperate fully with the United Nations to end the current impasse and to achieve progress toward a political solution".
In a report released a week ago, Kofi Annan, the UN secretary-general, said the 463-strong UN force known as MINURSO "continues to play a key stabilising and ceasefire monitoring role" and should have its mandate extended for another six months until October.
He recommended that Morocco engage in direct talks with the Algerian-backed Polisario Front without pre-conditions to settle the dispute over the Western Sahara, a former Spanish colony.
Annan said his personal envoy to the Western Sahara, Peter van Walsum, suggested that Algeria also be invited to join the talks.
Morocco considers Algeria a direct party in the dispute, as Algiers hosts the Polisario Front and backs its claim for independence.
The Western Sahara is Africa's longest-running territorial dispute. It goes back to 1975 when Morocco annexed the former Spanish colony after the Madrid Accords signed by Spain, Mauritania and Morocco.
Polisario staged a guerrilla war with Morocco in 1976, which ended in a 1991 UN-brokered ceasefire.
Morocco has recently proposed to provide the territories with a large amount of autonomy within the framework of a united and sovereign Morocco.
The front has rejected such proposals and calls for a referendum on self-determination.