The UN has admitted its response to the typhoon disaster in the Philippines has been too slow.
The agency says it let people down amid reports of desperate survivors short of food and water.
The UN's humanitarian chief Valerie Amos said the scale of the disaster and the logistics challenges it posed meant that six days on from the storm, some places remain without help.
"There are still areas that we have not been able to get to where people are in desperate need," she told reporters in Manila "I very much hope that over the next 48 hours that that will change significantly."
"I do feel that we have let people down."
"The situation is dismal. Those who have been able to leave have done so. Many more are trying. People are extremely desperate for help," Amos told reporters in Manila.
"We need to get assistance to them now. They are already saying it has taken too long to arrive. Ensuring a faster delivery is our... immediate priority."
However, she added: "There are thousands (of them) but we would never make the claim that we would be able to get to everyone."
Amos, who visited Tacloban on Wednesday to see the scale of the disaster, said her staff felt frustrated that supplies were stuck in the capital Manila.
The Philippines' shaky infrastructure took a battering in Typhoon Haiyan, one of the strongest storms ever to make landfall.
Many roads were left impassable, cluttered by debris from broken buildings that were destroyed when the ocean surged ashore.
The Philippines government said Wednesday that all roads were passable, but relief was still choked on Thursday, with fears over security after earlier attacks on aid convoys and widespread looting.
"Part of the job I have is to recognise the challenges we face but obviously (also) overcome those challenges and we have not been able to do that fast enough," conceded Amos.
UN Refugee Agency's Representative, Bernard Kerblat is in Tacloban
