Last year, under former US president Donald Trump, Washington recognised Moroccan sovereignty over Western Sahara -- after Rabat normalised relations with Israel -- sparking anger from the separatist Polisario Front.

The training, which the US Africa Command (Africom) says is its largest annual exercise, "marks the consecration of American recognition of the Moroccan Sahara", Prime Minister Saad-Eddine El Othmani said on Twitter last week.

Africom says the "African Lion" manoeuvres will involve more than 7,000 troops from nine nations, without giving further details of contributing countries.

Morocco laid claim to the Western Sahara, a former Spanish colony with rich phosphate resources and offshore fisheries, after Spain withdrew in 1975.

The Polisario Front took up arms to demand independence there, proclaiming the Sahrawi Arab Democratic Republic (SADR) in 1976 and fighting a 16-year war with Morocco.

Othmani said the exercises would take place at two sites in Western Sahara, including the eastern Mahbes region -- where Polisario regularly claim conflict in recent months -- and Dakhla, where Rabat plans to develop a large Atlantic port.

Sahrawi foreign minister Mohamed Salem Ould Salek however dismissed the report as a "completely false rumour".

"There will be no joint manoeuvrers in Western Sahara as part of 'African Lion 2021' in which US forces will participate," Salek told AFP.

"They will take place in the south of Moroccan territory, and within the internationally recognised borders of Morocco."

Morocco controls 80 percent of the territory, while the rest is run by the Polisario Front.

Rabat has offered Western Sahara autonomy, but maintains that the territory is a sovereign part of the kingdom.

Spain is understood not to be taking part in the exercises in Western Sahara.

Madrid has angered Rabat after Polisario Front leader Brahim Ghali was treated in a Spanish hospital for Covid-19 in April.

Last month, Spain was caught off guard when as many as 10,000 people surged into its tiny North African enclave of Ceuta as Moroccan border guards looked the other way, in what was widely seen as a punitive political gesture.