"In recent weeks, because of a standstill in cooperation between Palestinian authorities in Ramallah (the seat of government in the West Bank) and Gaza, imports of essential medical supplies have been reduced to a trickle, thus aggravating an already critical situation," the International Committee of the Red Cross said in a statement.
The ICRC said the situation was "extremely worrying" for several hundred severely ill patients in the coastal strip, including children suffering from cystic fibrosis who have not been able to take essential daily medicine for the past week.
"This is having a serious impact," said Eileen Daly, the ICRC's health coordinator for Gaza.
To make matters worse, Palestinian health workers have also been on strike since the end of August, which is hitting hospitals' ability to offer adequate care.
Surgical operations have decreased by 40 percent and hospital admissions are down 20 percent, the ICRC said.
The aid agency urged health authorities in both Ramallah and Gaza to take "urgent measures" to allow in medical supplies, and called on the Israeli authorities to "facilitate timely deliveries" of medical supplies and equipment to Gaza.
"Health issues should not be politicised," said Katharina Ritz, the ICRC's head of mission.
"Pragmatic solutions need to be found, because many lives are at stake."