A United Nations appeal for Yemen Wednesday is aiming to raise $4.27 billion to alleviate what it describes as the world’s worst humanitarian crisis, with 161,000 people likely to experience famine there in 2022.

The virtual pledging conference is co-hosted by Sweden and Switzerland. U.N. Secretary-General Antonio Guterres will address donors on the dire needs of the Arab world’s poorest country.

The conference comes as world attention is gripped by the war in Ukraine, which has overshadowed other humanitarian crisis across the world since the Russian invasion on Feb. 24 – raising concerns that that Yemen’s plight may be forgotten. Over 3 million people have fled Ukraine, which has seen Europe’s heaviest fighting since World War II.

Last year’s conference raised only some $1.7 billion for Yemen, out of $3.85 billion the U.N. had appealed for as the coronavirus pandemic and its devastating consequences hit economies around the globe. The U.N. chief called the 2021 result "disappointing."

Yemen’s war started in 2014 when the Iran-backed rebel Houthis seized the capital, Sanaa, and much of the country’s north. A Saudi-led, U.S.-backed coalition intervened months later to dislodge the rebels and restore the internationally recognized government.

The conflict has in recent years become a regional proxy war that has killed more than 150,000 people, including over 14,500 civilians. The war has also created the world’s worst humanitarian crisis, leaving millions suffering from food and medical care shortages and pushing the country to the brink of famine.

The majority of Yemen’s around 32 million people live in Houthi-held areas. The rebels have for years been implicated in aid theft and withholding for extortion.

U.N. experts earlier this year said they documented that the rebels provided or denied humanitarian aid to families "solely on the basis whether their children participated in fighting or to teachers on the basis of whether they taught the Houthi curriculum."

The U.N. Office for the Coordination of Humanitarian Affairs, or OCHA, has warned that a total of 19 million people are expected to face acute food insecurity by the second half of this year – an increase of around 20% compared to the first six months of 2021. Of them, 161,000 people are likely to experience famine, it said.

OCHA said that half of the country’s health facilities are shuttered or destroyed. It said the Yemeni currency, rial, lost 57% of its value in 2021 in government-run areas, while persistent fuel shortages drove up the prices of food and other basic commodities in the Houthi-controlled north.

It said 4.3 million Yemenis have been driven from their homes; around one-fifth of newly displaced in 2021 were in the energy-rich province of Marib which Houthis have attempted to for over a year, it said.

With the $4.27 billion for Yemen, the U.N. aims to provide support to 17.3 million people in 2022, out of the 23.4 million who need aid, OCHA said.