Morocco basked in US recognition of its sovereignty over Western Sahara Friday after outgoing President Donald Trump changed policy on the decades-old dispute in return for Rabat agreeing to normalise relations with Israel.

For the Polisario Front, which has campaigned for independence for the former Spanish colony since the 1970s, Trump's announcement marked a major setback and drew a promise to fight on until Moroccan forces withdraw.

But crucially, there was no immediate reaction from neighbouring Algeria, Morocco's regional rival and the Polisario's key foreign backer, whose support would be essential for any return to major fighting.

Moroccan Foreign Minister Nasser Bourita hailed US recognition of Western Sahara's "Moroccan identity" as a "historic diplomatic breakthrough".

"Several years of work" had been "crowned with the recognition of the United States, the major power on the (United Nations) Security Council," he told AFP in an interview.

Fellow permanent UNSC member Russia, historically close with Algeria, denounced the US move on Friday.

Deputy Foreign Minister Mikhail Bogdanov called the decision "unilateral" and "a violation of international law".

Morocco's official MAP news agency published commentaries from an array of Moroccan and foreign analysts trumpeting the US announcement as "vindication of the Moroccan cause" and the "beginning of the end for the Polisario gang".

Prince Moulay Hicham Alaoui, a cousin of King Mohammed VI, tweeted his appreciation of the "courageous" decision by Trump.

Support for the Palestinian cause runs deep in Morocco, but criticism of the monarch remains a red line even after a decade of reforms.

- 'Null and void' -

Islamist Prime Minister Saad-Eddine El Othmani, who has repeatedly spoken out against normalising relations with Israel in the past, made no immediate comment.

His adviser Nizar Khairoun welcomed US recognition that "the Sahara is Moroccan" but added: "Israel is an occupying power that usurps the rights of the Palestinians."

He was careful, however, to avoid any direct criticism of the king, who made the agreement to normalise ties with Israel in a telephone call with Trump.

The hashtag "#Normalisation is treason" was among the most popular on social media Friday, but it was far outstripped by the hashtag "#Sahara".

The Polisario dismissed Trump's announcement and vowed to fight on until Moroccan forces withdraw from all of Western Sahara.

"Fighting will continue until the total withdrawal of the Moroccan occupation troops," said Mohamed Salem Ould Salek, foreign minister of the Sahrawi Arab Democratic Republic (SADR), which Polisario leaders proclaimed in 1976.

The US decision was "null and void", Ould Salek said, emphasising that the international community "does not recognise and will not recognise any Moroccan sovereignty over Western Sahara".

Sovereignty "belongs exclusively to the Sahrawi people", he told AFP.

The Polisario had already announced last month that it regarded a 1991 ceasefire as over after Morocco sent