CAIRO — President Trump's decision to recognize Morocco's claims over the disputed Western Sahara threatens to fire up existing tensions in the region and deprive hundreds of thousands of the territory's inhabitants of their right to self-determination.

 It also, once again, pits the United States against most of the world.

 In exchange for Morocco’s agreement to begin normalizing ties with Israel, the United States on Thursday became the first and only major power to recognize Moroccan sovereignty over the Western Sahara region — an act that Morocco has sought for years.

 For the Moroccans, U.S. recognition is a key first step in persuading other major powers, including the European Union, Russia and China, to do the same, analysts said.

 “What this does is it adds a major world power in support of Morocco’s claims, which is something that Morocco has lacked until now,” said Samia Errazzouki, a former Moroccan journalist and current doctoral candidate who closely tracks the Western Sahara issue. “That is something that Morocco will likely use in future diplomatic engagements with other countries.”

 But getting more nations to recognize Morocco’s claims means going against U.N. resolutions that give the Western Sahara’s indigenous Sahrawi people and the Polisario Front, the pro-independence rebel movement fighting on their behalf, claims to the region. Today, 38 nations, mostly in Africa and Latin America, recognize or maintain diplomatic ties with the Sahrawi Democratic Arab Republic, which became a member of the African Union in 1984.

 “This will have no effect whatsoever on the legal nature of our question,” said Sidi Omar, the Polisario Front’s U.N. representative, referring to the U.S. recognition. “The United Nations doesn’t recognize Morocco’s sovereignty.”

 The U.S. decision comes amid rising tensions between Moroccan security forces and the Polisario Front, which is backed by neighboring Algeria. Last month, the rebels ended a 29-year-old cease-fire and declared a state of war after they accused Morocco of launching military operations in a buffer zone in the Western Sahara. Morocco said it acted because the rebels were allegedly stopping people and goods, and harassing U.N. peacekeeping troops, which the United Nations later denied.

 On Thursday, the animosity spilled into social media, with Omar, the Polisario envoy, declaring in a blistering tweet that Trump’s recognition “shows that Morocco’s regime is willing to sell its soul to maintain its illegal occupation of parts of Western Sahara.”

 In a statement, the rebels declared the agreement “a blatant violation of the United Nations charter and the resolutions of international legitimacy.” The move, the group added, “obstructs efforts by the international community to find a solution to the conflict.”

The Western Sahara region, a former Spanish colony, was annexed by Morocco in 1975. That touched off a 16-year conflict between the rebels and the Moroccan government that lasted until the United Nations brokered a truce in 1991. Morocco now controls roughly three-quarters of the Western Sahara, a stretch of territory in the country’s southwest, while the Polisario and Sahrawi Republic oversee the rest. The United Nations recognizes the entire area as a “non-self-governing territory.”

 More than 100,000 people have fled the conflict and repression in the Western Sahara and now live in desolate conditions as refugees in the Algerian desert. Many have placed their hopes on the promise of a referendum on independence, which the United Nations is mandated to oversee but has yet to take place. Their future is now more uncertain than ever.

 With the United States wielding veto power in the U.N. Security Council, the prospects for a referendum are even more diminished. And if more governments follow the U.S. stance, international recognition of an independent Sahrawi nation will be elusive.

 “It puts the nail in the coffin in terms of any possible referendum,” said Errazzouki. “Without a referendum, it’s going to have an impact on what future steps the Polisario Front and the refugees will take. And as we have seen in the past few months, war is not off the table.”

 Tensions could spill across borders. Algeria, the rebels’ main benefactor, has its own internal problems to deal with, including an economic crisis, political and social unrest and a president who has been hospitalized for covid-19 since late October. But the country could intervene if the Polisario Front is actively targeted.

“Morocco, emboldened by what is clearly a U.S. endorsement, will feel free to pursue its war effort against the Polisario Front, which may appeal for the intervention of Algeria, its main foreign backer,” said Hamish Kinnear, a North Africa analyst at Verisk Maplecroft, a political risk consultancy, in an emailed analysis.

 Kinnear added that U.S. recognition “is unlikely to lead to an overnight change in the position of major countries,” noting that even close allies of Morocco, such as France, agree with the United Nations on the status of the Western Sahara.

 “Whatever other countries choose to do, that will be their own business,” said Omar, adding: “We will continue our struggle until we achieve our freedom.”

 The Polisario Front, he said, remains hopeful that the incoming administration of President-elect Joe Biden will reverse the “decision taken by Donald Trump, which is in violation of basic norms of international law.” But Kinnear and other analysts said such a move is unlikely because it would probably torpedo Morocco’s normalization with Israel.