Monrovia (AFP) - A second deployment of United States troops arrived in Liberia on Sunday as part of an eventual mission of 3,000 soldiers helping its beleaguered health services battle the Ebola outbreak.

The contingent will be focused on training local health workers and setting up facilities to help Liberia and its neighbours halt the spread of the epidemic, which has left more than 2,600 dead across west Africa.

"Some American troops came soon this morning. They arrived with tactical jeeps," a source at Roberts international airport, near Monrovia, told AFP.

The source was unable to give the size of the unit, which arrived in one aircraft, but the US has already announced it was planning to send 45 troops over the weekend.

Pentagon spokesman Rear Admiral John Kirby told reporters on Friday a C-17 aircraft with equipment and seven service members landed in Liberia on Thursday, with two more cargo planes due to follow.

The small team will set up a headquarters for Major General Darryl Williams, who will oversee the US mission to train local health workers and establish additional medical facilities, he said.

Military engineers are due to build new Ebola treatment centres in affected areas, Washington said last week, while US officials will help recruit medical personnel to work at the units.

The Pentagon has said the troops will have no direct contact with patients.

President Barack Obama unveiled the troop deployment to west Africa last week, issuing an international call to action to prevent the virus from spreading "exponentially".

Liberian President Ellen Johnson Sirleaf has welcomed the US mission and said she hoped Washington's move would prompt other countries to provide more support to address the epidemic.

The UN Security Council has called the virus a threat to world peace.

The fever it unleashes can kill victims within days, causing severe muscle pain, weakness, vomiting and diarrhoea -- in many cases shutting down organs and causing unstoppable bleeding.