The UN said it wanted to support government efforts to provide emergency relief over the next three months.
Riot police have clashed with people trying to leave the capital Kathmandu, and there are reports of villagers blocking trucks carrying supplies.
The government says it has been overwhelmed by the disaster.
Saturday’s 7.8-magnitude quake killed more than 5,000 people and injured at least 10,000.
The UN says more than eight million people have been affected and some 70,000 houses have been destroyed.
Although aid is starting to get through, some people in remote areas closest to the epicentre of the quake are stranded without shelter, food or water.
“Although I am heartened and encouraged by the progress of the response to date, efforts need to be maintained and stepped up to ensure vital assistance reaches all the affected, especially those in the remote areas,” said the UN’s resident co-ordinator for Nepal, Jamie McGoldrick
Some helicopter crews who have managed to land in isolated communities have been faced with desperate villagers pleading to be airlifted to safety.
In Kathmandu on Wednesday, riot police clashed with protesters angry at a lack of transport out of the city and delays in distributing aid.
Thousands were waiting for buses to take them to rural areas.
“We’ve been left starving in the cold and the best this government can give us is this queue,” said one resident, Rajana, as she queued for a bus to her home village.
Witnesses said a truck carrying drinking water was forced off the road and protesters climbed on top of it, throwing the bottles into the crowd.
As tempers flared, columns of riot police stood behind rolls of razor wire as protesters surged into the street.
In the village of Sangachowk, angry villagers blocked the main road with tyres and stopped trucks of rice and other aid headed for other areas, Reuters reported.
“We have been given no food by the government,” said villager Udhav Giri.
“Trucks carrying rice go past and don’t stop. The district headquarters is getting all the food.”
The villagers also reportedly blocked a convoy of army trucks loaded with relief supplies, leading to a tense standoff with armed soldiers.
There were more angry scenes in Dolakha, east of Kathmandu, when residents smashed the windows of a local administrative building, Chief District Officer Prem Lal Lamichhane said.
“Over 200,000 people are homeless. We’ve been told that materials are on their way, but we haven’t received them yet,” he added.
However, there were some signs on Wednesday that parts of the capital were returning to normal.
Some people have decided to return to their homes, having spent four nights in the open. Cash machines have been refilled and some street vendors have once again started trading.