U.S. President Donald Trump has reaffirmed support for Morocco's sovereignty over Western Sahara, saying a Moroccan autonomy plan for the territory was the sole solution to the disputed region, state news agency MAP said on Saturday.

The long-frozen conflict pits Morocco, which considers the territory as its own, against the Algeria-backed Polisario Front, which seeks an independent state there.

Trump at the end of his first term in office recognised the Moroccan claims to Western Sahara, which has phosphate reserves and rich fishing grounds, as part of a deal under which Morocco agreed to normalise its relations with Israel.

His secretary of state, Marco Rubio, made clear in April that support for Morocco on the issue remained U.S. policy, but these were Trump's first quoted remarks on the dispute during his second term.

"I also reiterate that the United States recognises Moroccan sovereignty over Western Sahara and supports Morocco's serious, credible and realistic autonomy proposal as the only basis for a just and lasting solution to the dispute," MAP quoted Trump as saying in a message to Morocco's King Mohammed VI.

"Together we are advancing shared priorities for peace and security in the region, including by building on the Abraham Accords, combating terrorism and expanding commercial cooperation," Trump said.

As part of the Abraham Accords signed during Trump's first term, four Muslim-majority countries agreed to normalise diplomatic relations with Israel after U.S. mediation.

In June this year, Britain became the third permanent member of the U.N. Security Council to back an autonomy plan under Moroccan sovereignty for the territory after the U.S. and France.

Algeria, which has recognised the self-declared Sahrawi Republic, has refused to take part in roundtables convened by the U.N. envoy to Western Sahara and insists on holding a referendum with independence as an option.