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

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

The U.N.'s humanitarian arm, OCHA, points 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.

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.