Aid agencies began to vaccinate Liberian refugees aboard a ship off Sierra Leone on Friday while U.N. officials tried to convince officials to let them disembark.

One thousand other Liberians who want to flee their war-torn capital Monrovia remained stuck in the city’s port awaiting passage to neighboring countries.

The port was heavily guarded by African peacekeepers.

The fleeing Liberians have endured voyages on crowded, leaky vessels only to be turned away or accepted reluctantly by Liberia’s neighbors, who are fed up with the endless factional fighting and have troubles of their own.

The U.N. High Commissioner for Refugees was negotiating with authorities in Sierra Leone who have refused to let 142 Liberians on board the Victory Reefer disembark, said UNHCR spokesman Ahmad Fawzi.

Aid agencies began vaccinating the refugees against measles and other diseases while their fate is being decided.