Donors in April pledged close to $1.1 billion (981,500 euros) in aid to war-torn Yemen, which the UN Office for the Coordination of Humanitarian Affairs calls the "largest humanitarian crisis in the world," AFP reported.
But "only 25 percent of aid pledged to the UN refugee agency and 29 percent of aid pledged to the UN's humanitarian response plan have been delivered so far," UNHCR's Yemen spokesperson Shabia Mantoo told AFP.
Some 19 million people are in need of aid in Yemen, with 10.3 million requiring immediate assistance to "save or sustain their lives", according to the United Nations.
Riyadh has been incessantly pounding Yemen since 2015 in a bid to reinstall the country’s ex-government and crush the Houthi Ansarullah movement.
Saudi Arabia that carries out airstrikes almost daily has killed at least 10,000 people in Yemen, and hunger and disease are rife there.
Looming famine and an outbreak of cholera in Yemen, the most impoverished country in the region long before the war, are taking their toll on the population.
"Conditions are only worsening. The cholera rates are alarming, health facilities are struggling to remain functional, millions across the country are food insecure and facing prolonged displacement from their homes," Mantoo said.
The International Committee of the Red Cross on Wednesday warned that Yemen's health system is on the "brink of collapse".
The organization said 5,000 new suspected cases of cholera have been reported every day over the past two weeks in Yemen, where an outbreak of the waterborne disease has killed more than 900 people since April 27.
"Two years of armed conflict have brought Yemen's health system to the brink of collapse," said ICRC's head of delegation in Yemen Alexandre Faite.
"This cholera outbreak is only the most recent, and most visible, proof that people and structures have been seriously weakened by the way this conflict is being waged," Faite said.
A quarter of a million people are expected to contract cholera within six months, according to the World Health Organization.