PRESIDENT Barack Obama says about 100 US military personnel have been deployed to the west African nation of Niger.

In a letter to Congress on Friday, Obama said the forces will focus on "intelligence sharing" with French troops fighting Islamist militants in neighbouring Mali.

He said the American forces have been deployed with weapons "for the purpose of providing their own force protection and security".

The US and Niger signed an agreement last month spelling out legal protections and obligations of Americans who might operate from the African nation.

But US officials declined at the time to discuss specific plans for a military presence there.

The Pentagon is also considering plans to base unarmed spy drones in Niger to boost its ability to see what is happening in the region.