The United Nations said the lives of millions of Ethiopians in the north of the country were threatened because the aid did not reach the conflict-affected areas.
In a stern warning, it said that the Tigray area had actually been blocked for aid.
A government spokesman denied that supplies are being stopped.
Ten months of fighting between the Union army and its allies and the Tigray rebels left many people in urgent need of assistance.
“The lives of millions of civilians… depend on our ability to provide them with food, nutritional supplies, medicines and other important aids,” Said Grant Letty, the United Nations Acting Humanitarian Coordinator for Ethiopia.
The United Nations estimates that 5.2 million people will need emergency assistance if “the worst famine in the world in decades” is to be avoided.
Mr. Leaity said that although aid can now be transferred within Tigray more easily than before, there are still problems in bringing aid trucks into the area.
Currently the only feasible land route is through the neighbouring Afar area, but he said logistic and bureaucratic obstacles have caused long delays.
Rescuers said that 100 trucks carrying food need to enter Tigray every day, but no truck has passed through since August 22.
Aid agencies have used up food for distribution in most areas.
Mr. Leaity called on the Ethiopian government to allow unhindered access to aid materials and personnel.
In the past, the government denied blocking aid, but expressed concern about security issues.
According to Reuters, the prime minister’s spokesperson, Billing Seyoum, told reporters in the capital Addis Ababa on Thursday that the truck was “heading” to Tigray.
She added that the number of checkpoints has actually been reduced.
The conflict began in November last year after months of disputes between the government of Prime Minister Abiy Ahmed and the leaders of Tigray’s main political party, the Tigray People’s Liberation Front (TPLF).
It is believed that thousands were killed, millions were forced to leave their homes, and some fled to Sudan.
The fighting has now spread to neighboring Ethiopian regions Afar and Amhara.
Earlier this week, the head of the humanitarian agency of the US government stated that the Tigray army had ransacked its warehouse in Amhara.
TPLF, described by the government as a terrorist organization, did not respond to these allegations.