Ursula Mueller, UN assistant secretary-general for humanitarian affairs, told the Security Council that "only 34 percent of plan requirements have been met," while "at this time last year, the plan was 65 percent funded."
At a UN conference in February, donors pledged US$2.6 billion for Yemen humanitarian aid, led by Saudi Arabia and the United Arab Emirates.
The amount marked a 30-percent increase from that in 2018.
While nearly all donors have paid most or all of their 2019 pledges, "the largest donors ... have so far paid only a modest share of what they promised," said Mueller.
In the world's largest humanitarian operation, agencies working through the UN response plan are assisting an average of 12 million Yemeni people every month.
"But much of this is about to stop" due to the inadequate funding, said the UN official.
She cited the cancellation of vaccination campaigns, supplies for health facilities and cholera prevention programs last month.
She further said water and sanitation programs will stop in four governorates in the next few days, which will leave 300,000 displaced people at extreme risk of cholera.
"By the end of September, WASH (Water, Sanitation and Hygiene) programs for another one million people will also close," she said, adding "in September, we will be forced to close life-saving programs for 2.5 million malnourished children."
Meanwhile, the UN official addressed the issue of humanitarian access, saying agencies continue to face severe restrictions in Yemen.
She said in the north, Houthi-affiliated authorities have imposed dozens of formal and informal directives, and as a result, over 100 projects are awaiting agreement by these authorities.
In government-controlled areas, she said, official regulations are less heavy, but delays persist in getting humanitarian projects up and running.
Moreover, Mueller called for all parties to uphold international humanitarian law, urging all feasible steps to be taken to avoid harm to civilians and civilian infrastructure.
"This includes verifying targets, taking precautions in the choice of weapons and cancelling an attack if it is expected to cause disproportionate civilian harm," she stressed.
