The United Nations secretary-general and high-ranking government officials from dozens of countries were meeting Tuesday in Geneva to drum up funds for war-torn Yemen, considered one of the world's greatest humanitarian crises.

Antonio Guterres and top diplomats from Switzerland and Sweden are co-hosting a pledging conference in the Swiss city that's aimed at helping assemble $2.1 billion in a U.N. relief appeal that was launched this year.

The U.N.'s humanitarian arm, OCHA, has pointed to "an alarming 18.8 million people in need of humanitarian or protection assistance" in Yemen.

Yemen's war has killed more than 10,000 civilians and pushed the Arab world's poorest nation to the brink of famine. The conflict has also led to the displacement of some 3 million Yemenis.

Humanitarian aid groups have sought greater access to people in need, a halt to airstrikes by a Saudi-led, Western-backed coalition fighting Yemen's Shiite rebels, and greater respect for international humanitarian law.

The war pits the coalition of mostly Arab Sunni countries against the Shiite rebels known as Houthis, who seized Yemen's capital and some other areas in 2014 and forced the internationally-recognized government to flee the country.

In a dramatic joint appeal, the U.N. children's agency and the World Food Program said 7 million people in Yemen don't know where their next meal will come from and are in desperate need of food assistance.

Nearly 2.2 million children are malnourished, including half a million who are severely malnourished and at imminent risk of death if they do not receive urgent care and specialized treatment, UNICEF and WFP said in a statement released Tuesday.

"Without further action from parties to the conflict and the international community, Yemen is at a serious risk of plunging into famine - with even more children's lives hanging in the balance," said Geert Cappelaere, UNICEF's director for Mideast and North Africa. "We are in a race against time."