Hundreds of thousands of Yemenis face what experts fear could be one of the world's worst coronavirus outbreaks, raising concerns of a staggering death toll after the United Nations began cutting aid to the war-torn nation.

The cuts came after UN appeals for $2.42 billion in funding fell short by about 50% this week.

"In the countdown to closure there will have to be much wider cuts to Yemen at a time when the country is now facing the growing impact of the virus pandemic on people who are already badly malnourished and ill equipped to cope with it," Lise Grande, the head of the UN's humanitarian operations in Yemen told CNN, in a phone call from Sana'a on Wednesday, the capital of the divided nation.

"General health services in 189 of the country's 369 hospitals start to close in three weeks. Water and sanitation services for 8.5 million people, including 3 million children, close in three weeks. Nutrition support for 2.5 million malnourished starving children will start to close in eight to 10 weeks," she warned.

On Tuesday this week donors pledged $1.35 billion of the $2.42 billion the UN said Yemen needed in a virtual conference.

 "The worst-case scenario -- which is the one we're facing now -- means that the death toll from the virus could exceed the combined toll of war, disease and hunger over the last five years [in Yemen]," Grande told CNN.

According to Armed Conflict Location and Event Data Project, just over 112,000 people have been killed in Yemen's civil war over five years -- among the dead are 12,690 civilians.

Estimates for the numbers of people who have died from disease and malnutrition in the country have varied widely. But the UN and other aid organizations are delivering humanitarian assistance to 10 million Yemenis. A cholera epidemic has, the UN believes, already infected 110,000 people this year.

Four out of five Yemenis need "lifesaving aid," UN Secretary-General Antonio Guterres said at the conference on Tuesday, adding that Yemen faced one of the highest death tolls in the world from Covid-19. The country has a negligible capacity to test for coronavirus but medical aid agencies also believe the scale of infections could be vast.

This week health services for women giving birth in 150 hospitals supported by the UN were closed in the first wave of the cuts after the funding conference.

Yemen's five-year civil war has pitted Houthi rebels against the internationally recognized government, which has been backed by the UAE and Saudi Arabia.

Earlier this year the Emiratis pulled their military out of the conflict but continues to back the government, which is in exile in Saudi Arabia. Riyadh, meanwhile, has continued to back and fund tribal militias and its air force has had a punishing effect on the ground.

Much of the shortfall in new funding is being blamed on the apparent failure of Saudi Arabia, the United Arab Emirates and Kuwait to come forward with a combined pledge which, in previous years, has been for about $1.5 billion. This year the UAE and Kuwait did not offer any funds to the UN effort and Saudi Arabia offered $500 million of which $300 million was to be earmarked specifically for the UN.

Saudi Arabia has been keen to get out of the quicksand since late last year. The war has undermined support for Saudi Arabia in Washington, where renewed arms supplies to the Kingdom from the US have only been possible as a result of the Trump administration's use of emergency powers to get around a block on arms exports to Saudi Arabia imposed by Congress.

Some diplomats believe that the cut in funding to the UN by Gulf countries may be, in part, an attempt to force the Houthis to peace talks.

Aid to areas under Houthi control has frequently been diverted and manipulated by the rebel administration in Sanaa. The UN's World Food Programme has frequently complained about the Houthis' diversion of food -- and the US cut funding to the program to force improvement.

The US support, $225 million, to the WFP was only returned recently after the Houthis agreed to stop aid workers from being harassed and a wide range of "taxes" on aid coming into the area under their control.

Saudi Arabia and the UAE say they want to continue to help Yemen with aid -- but insist it should not be diverted to the Houthi war effort. In the Emirates it is understood that the government is trying to find ways to continue to fund aid operations.

"The UAE has spared no effort in providing medical assistance to support countries affected by Covid-19 by cooperating with international organizations, wherein UAE assistance amounted to $135 million from the beginning of March until the end of May," Reem al Hashimy, the Emirati minister for international cooperation said in a statement to CNN.