The U.N. Office for the Coordination of Humanitarian Affairs said in a statement that a "changing operating context" in the wake of Taliban administration restrictions on female aid workers had contributed to the revised plan.
Taliban authorities have issued several orders barring many Afghan female NGO and United Nations employees from being able to work, which aid agencies have warned would severely hamper delivery in the religiously conservative nation.
"The recent bans on Afghan women working for... NGOs and the U.N. have added yet another layer of complexity to what is already an incredibly challenging protection environment, and further constrained the operational capacity of partners," the U.N. statement said.
Afghanistan remains one of the world's worst humanitarian crises, the statement added, with more than two-thirds of the population in need of humanitarian assistance.
Some humanitarian officials and diplomats have warned of a potential decline in funding to the war-ravaged nation due to the Taliban restrictions on female workers and donor governments assessing competing global crises and economic priorities.
It was not clear how much of the revised budget would be funded by foreign donors.
Global humanitarian appeals often fall short of the total amount requested. In 2022, the humanitarian response plan was budgeted at $4.4 billion and received around $3.2 billion. The U.N. says the number of people in need has grown since last year.
The United Nations' development agency in April predicted Afghanistan's economy would contract and inflation would rise if there were a 30% drop in aid.