|Haiti's government says at least 50,000 people have died as a result of the earthquake [REUTERS]
Thousands of people in Haiti remain desperate for food, water and medical care as relief workers struggle to distribute aid supplies after a devastating earthquake.
International relief organisations and teams from the United Nations are finding it difficult to move tonnes of supplies from the airport near Port-au-Prince, the capital, for distribution across the Caribbean nation devastated by Tuesday's quake.
Haiti's government says that at least 50,000 people have died as a result of the magnitude 7.0 quake. Some relief organisations though say the death toll could be as high as 200,000.
Al Jazeera's Zeina Khodr, reporting from the centre of the capital, said the situation is desperate for many people left homeless.
"People here are not receiving any aid whatsover. They lack food, they lack water. During the night you can hear them sing, trying to comfort each other.
She said many people have lost loved ones or at least know people who have died in this earthquake.
"Some people say they don't even know if their brother or sister is alive [because] many people remain trapped underneath the rubble. But it seems people are losing hope at this point of finding survivors."
Khodr said the immediate priority now is to deliver aid to the victims as soon as possible.
But she said some aid agencies have complained of delays in reaching the survivors and of aid being turned away from the airport.
Haiti has handed over control of the airport to the United States, but some aid workers have complained that the US is giving priority to military aircraft instead of relief flights.
Aid flights have been arriving at the airport faster than ground crews can unload them, prompting aviation authorities to restrict non-military flights for fear that jets would run out of fuel while waiting to land.
Christopher Loundermon, a US Navy spokesman for Joint Task Force Haiti, said US teams on the ground understand the frustration felt by many Haitians and are working to meet their needs.
"We are doing our best," he told Al Jazeera.
"If we get more forces in, we will also be able to increase the amount of supplies that are delivered. If other organisations and other countries are able to provide more assistance, more will get out to the people of Haiti.
"The United States is here to help [the people of Haiti] and we'll be here as long as it takes."
Sebastian Walker, another Al Jazeera correspondent in Port-au-Prince, said 200 tonnes of aid have piled up at the airport.
"This comes down to the complex issue of who is in charge here. The US military has a great deal of control over the number of flights that are landing here," he said.
"We heard that a UN flight carrying aid equipment had to be diverted because the US was landing its own aircraft there. The question of just who makes the decision over how to distribute the aid seems to be what is holding up the supplies.
"At this point, there are thousands camped out in the streets...These people have been sitting out here for days now, and they say that they have not received the food and aid that is ready to be delivered."
Lorries have been trying to collect the bodies that have been visible on the streets across Port-au-Prince for burial in mass graves outside the city.
If the casualty figures are accurate, Tuesday's quake would be one of the 10 deadliest on record.
'Difficult days ahead'
About 40,000 bodies have already been buried, while the bodies of another 2,000 victims have been incinerated at one of Port-au-Prince's rubbish dumps.
Barack Obama, the US president, on Saturday urged patience with the relief operation, saying there would be "many difficult days ahead".
Flanked by his predecessors George Bush and Bill Clinton, Obama also announced a national drive to raise money to help survivors.
"President Bush and Clinton will help the American people to do their part, because responding to disaster is the work of all of us", Obama said, speaking in the White House Rose Garden.
Bush told journalists that the best way to help Haiti was "just send your cash", and announced a website to help fund-raising - the Clinton-Bush Haiti Fund.
The US plans to send 10,000 US troops to Haiti to help distribute aid and prevent potential rioting among survivors, Mike Mullen, the chairman of the US joint chiefs of staff, said.
Source: Al Jazeera and agencies