U.S. Deputy Secretary of State Christopher Landau said on Thursday that Washington backs investments in disputed Western Sahara, where Morocco has been building infrastructure to attract foreign investors.

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.

"We will support U.S. companies looking to invest and do business in all of Morocco, including Western Sahara," Landau said on X, following talks with Moroccan Foreign Minister Nasser Bourita.

Morocco, which has a free trade agreement and a trade deficit with the U.S., has the lowest "reciprocal" tariff rate imposed by the Trump administration - of 10%.

Rabat has in recent years ramped up investments in Western Sahara, including roads, renewable energy projects, phosphates mining and a port worth $1 billion.

U.S. President Donald Trump reaffirmed support for Morocco's sovereignty over Western Sahara in July, saying a Moroccan autonomy plan for the territory was the sole solution.

France took a similar move recognising Rabat's sovereignty over the territory and greenlighting investments there.

In June, the UK became the third Security Council member to back autonomy under Moroccan sovereignty as a solution to the dispute.

Algeria and the Polisario denounced Western nations that back the autonomy plan and insist on holding a referendum with independence as an option.

The UN said the conflict was of low intensity and urged the parties to negotiate a political and mutually acceptable solution.