The US military has scaled back plans for its mission in Liberia to fight the Ebola outbreak, and will deploy a maximum of 3,000 troops instead of 4,000, a commander said Wednesday.

But the move did not signal less concern about the threat posed by the epidemic, even as the rate of infection has slowed, the commander and other officials said.

The decision came after US officers found local contractors could perform some of the required construction work for the mission and as private aid organizations sent in workers to help, eliminating the need for another thousand soldiers, General Gary Valesky, head of the American military contingent in Liberia, told reporters in a telephone conference.

There are nearly 2,200 US troops in Liberia today and the Pentagon had planned to deploy up to 4,000 but now the target level was at 3,000, Valesky said.

"What we found working with USAID (US Agency for International Development) and the government of Liberia was there's a lot of capacity here that we didn't know about before," the general said.

"And so that enabled us to reduce the forces that we thought we originally had to bring. And so right around 3,000 is what we're looking at," he said.

However US ambassador to Liberia Deborah Malac warned it was crucial to remain vigilant.

"We are not out of the woods by any stretch of the imagination," she said at the same briefing.

The number of cases continues to increase every day but "the rate of increase is much lower than it has been over the last couple of months," she said.

The World Health Organization announced Wednesday the Ebola epidemic has now claimed 5,160 lives, almost entirely in West Africa. And in Mali, the death of an Islamic cleric dashed hopes that the country was free of the highly-infectious pathogen.

The US military is setting up several mobile test labs, a field hospital for local health workers and up to 17 Ebola treatment units across Liberia, but American troops are not in contact with patients directly.

No US military service members have shown symptoms from the virus so far, Valesky said.