Spain has written to the Moroccan king, Mohammed VI agreeing that having Western Sahara operate autonomously under Rabat’s rule is “the most serious, realistic and credible” initiative for resolving a decades-long dispute over the vast African territory.

This marked an enormous departure from Spain’s earlier stance of considering Morocco’s grip on Western Sahara an occupation. The shift followed months of frosty diplomatic relations and led to the announcement of a flurry of visits by Spanish officials to its southern neighbour.

The United Nations has continued to regard Madrid as the colonial administrative power for Western Sahara, even after its annexation by Morocco immediately after Spain abandoned its African province in 1975. Over the years, the Spanish government’s official position and the European Union’s have been to support a U.N.-sponsored referendum in Western Sahara.

But according to a statement issued by Morocco’s royal palace, Spanish Prime Minister Pedro Sánchez recognised “the importance of the Sahara issue for Morocco” in a letter to King Mohammed VI.

In his message to the Moroccan King, the President of the Spanish Government also stressed that "the two countries are inextricably linked by affections, history, geography, interests and shared friendship”.

Mr Sanchez said he was "convinced that the destinies of both peoples are linked as well" and that "the prosperity of Morocco is linked to that of Spain, and vice versa. Spain considers the autonomy initiative presented by Morocco in 2007 as the basis, the most serious, realistic and credible, for resolving the dispute”.

Spanish Foreign Minister José Manuel Albares confirmed the Moroccan announcement. “Today we begin a new stage in our relations with Morocco and finally close a crisis with a strategic partner,” he told reporters.

He added that the new chapter was “based on mutual respect, compliance with agreements, the absence of unilateral actions and transparency and permanent communication.”

Albares, the Spanish Foreign Minister, has been invited for meetings in Rabat later this month and officials were scheduling a visit by Sánchez himself, the Moroccan ministry of foreign affairs said.

In its statement, the Spanish government welcomed the invitations and said it wanted to face “common challenges” together with Rabat, “especially cooperation in the management of migratory flows in the Mediterranean and the Atlantic.”

According to the Moroccan royal palace, in his message to the king, Sánchez wrote that Spain’s goal is “to act with the absolute transparency that corresponds to a great friend and ally.”

Relations between Spain and Morocco hit a historical low last year after Spain secretly hosted for medical treatment the leader of the polisario.