"You have been assigned a difficult task to bring Liberia back to normalcy," said General Daniel Opande in a farewell address to the 675 Nigerian troops.

The troops were in high spirits, clapping and singing songs, as they waited to board the helicopters -- four Mi-8s and one Mi-26 -- to the neighboring west African country.

"We shall be watching what you are doing, and I am sure you will succeed," said Opande, who commands the UN peacekeeping force in Sierra Leone, from which the Nigerian soldiers are being detached to serve in Liberia on behalf of the west African regional group ECOWAS.

Alan Doss, a UN envoy who was also on hand for the departure, told the troops: "I wish you godspeed in your historic mission. Liberia needs your help. ... You are the star of this big operation and I am sure you will be successful."

Armored personnel carriers, Land Rovers and vans marked ECOMIL -- the acronym of the west African peacekeeping force for Liberia -- were seen being loaded into the Mi-26 helicopter.

The advance force will include 18 officers, led by Nigerian General Festus Okonkwo.

The troops are expected to touch down around 9:00 am (0900 GMT) at Robertsfield Airport, 40 kilometres (25 miles) outside Monrovia, according to military sources.

Additional deployments over the coming days will bring the initial deployment to some 1,500.

In Monrovia the Nigerians are expected to be greeted with joy by a population that has suffered more than a decade of civil conflict topped off since June 5 by attacks on the capital itself.

Both the government of President Charles Taylor -- who has vowed to step down on August 11 -- and the rebel movement Liberians United for Reconciliation and Democracy (LURD) have promised to work with the peacekeepers.

Both sides have, however, breached previous ceasefire agreements, and after a weekend in which Taylor launched a failed but bloody bid to recapture Monrovia's seaport, few observers expect an easy transition to peace.

Despite the doubts, news that the Economic Community of West African States' (ECOWAS) peace mission was going ahead inspired a mood of anxious optimism in a city gripped by hunger and menaced by disease.

The mission has been set up by ECOWAS but has some international financial backing and has been given a tough UN mandate to stabilise Liberia.

On Saturday Taylor -- a former warlord who fought his own way to power in a bloody civil war and had turned Liberia into a breeding ground for regional instability -- agreed to step down.

Nigeria, west Africa's economic and military giant, had offered Taylor asylum if he agreed to resign as leader of a nation that has suffered more than a decade of war and served as a breeding ground for regional instability.

WAR.WIRE