The UN warned fuel shortages threaten to halt all relief operations in Yemen "within days" as Saudi-led air strikes and ground fighting killed 47 people in second city Aden.
Gulf Arab states rejected any neutral venue for UN-brokered peace talks as a confidential UN report supported their allegations that regional rival Tehran had been arming Yemen's Huthi Shiite rebels since 2009.
Yemen was the poorest Arab country even before the rebellion against now exiled President Abedrabbo Mansour Hadi escalated last year and UN agencies said on Thursday that millions were at risk from any halt to food distributions.
The bombing campaign launched by a Saudi-led coalition of Sunni Arab states on March 26 has virtually halted the delivery of both humanitarian aid and commercial goods, including fuel.
UN chief Ban Ki-moon said the lack of fuel was preventing agencies on the ground from distributing even those stocks already inside the country, most of which are in the hands of rebels who are under a UN arms embargo.