Since late July, U.N. negotiators have tried to achieve a new round of negotiations. Polisario says it is ready to talk but the timing is complicated.
Polisario has a new leader, Brahim Ghali, following the death of its founder Mohammed Abdelaziz in July, while U.N. Secretary-General Ban Ki-moon will be replaced on Jan. 1 by Antonio Guterres.
On top of this, Morocco says the U.N. envoy to Western Sahara, Christopher Ross, cannot visit Rabat until a new government has been formed following elections in September and it has hosted a U.N. climate change conference this month.
In the meantime, Rabat is lobbying to rejoin the African Union, hoping to win support from the bloc for a plan put forward by King Mohammed which offers the region autonomy under Moroccan sovereignty. Rabat abandoned the AU three decades ago in protest when it recognised Polisario.
Much of the impasse reflects splits in the U.N. Security Council, which has been unable to force either side to accept proposals. France backs Morocco while the United States is more cautious but calls the king's plan "credible and realistic". Outside the five permanent members, Venezuela and Angola are more supportive of Polisario.
Mohamed Hadad, Polisario's U.N. coordinator, said the ball was with the Council. "The Security Council must consider there is a challenge to peace, they must give attention to this conflict," he said.
Rabat dismisses Polisario's insistence that the referendum be held, saying this plan is no longer specifically mentioned in U.N. resolutions. "Why do we need to go back to 1991?" said one Moroccan official source.
Western diplomats and a U.N. source said Morocco's move in Guerguerat appeared to be a flexing of muscles to test the new Polisario leadership while it plays for time diplomatically.
"They wanted to demonstrate to us all that they can move beyond the berm, which is a dangerous initiative to take," the U.N. source said. "In the absence of a negotiations process, we will see more and more of this."
Morocco rejects those accusations. "Polisario reacted, and violated the ceasefire by bringing in military," the Moroccan source said.