The international community will gather on Tuesday to try to raise more than $4bn to help alleviate the suffering and famine caused by Yemen’s civil war, but will find itself heavily dependent on three combatants in the conflict – Saudi Arabia, the United Arab Emirates and the US – to reach its fundraising target for 2019.

The $4.2bn (£3.2bn) target for 2019 – the largest sum sought for any single year since the start of the civil war in 2015 and an increase of 33 % on last year – will be the focus of an all-day pledging conference in Geneva.

Yemen has been gripped by hunger since conflict broke out between Iranian-supported Houthi rebels and a Saudi-led coalition supporting the UN-backed Yemen government.

The Geneva conference chaired by the UN secretary-general António Guterres comes at a potentially critical inflection point in the conflict, as a UN-brokered phased troop withdrawal agreement – agreed in principle in Stockholm in December – is due to be implemented on the ground for the first time this week. The withdrawals are set to occur in three ports, including the key Red Sea port of Hodeidah.

'Yemenis are left so poor they kill themselves before the hunger does' Read more

The summit comes after reports that delays to scheduled withdrawals of Houthi troops had led to clashes between the two sides in southern Hodeidah, something that would represent a setback to the Stockholm agreement.

The UN says about 20 million people need help to secure food this year in Yemen, including nearly 10 million who are just a step away from famine. Nearly 240,000 are facing “catastrophic levels of hunger”, it says.

Last week Mark Lowcock, the UN coordinator for humanitarian relief, told the UN security council: “Among the many challenges the aid operation faces, funding is quickly becoming the biggest. We expect current resources to be used up by the end of March – just six weeks from now”. More than 250 humanitarian organisations are operating in the country.

Britain’s Department for International Development (DfID) announced at the weekend it would provide a further £200m in 2019, taking its total aid donations to £800m since the civil war started.

But it is calculated that in 2018 nearly 60% of the aid to alleviate suffering in Yemen came from Saudi Arabia, the UAE and the US, the three countries most active in helping the UN-recognised government of Yemen to defeat an Iranian-supported insurgency run by the Houthis.

They are likely to be the dominant donors again this year, highlighting the paradox that those leading the aerial bombing campaign are doing most to alleviate some of its consequences.

In a statement ahead of the Geneva conference, Unicef’s Middle East and North Africa director, Geert Cappelaere, said: “Not enough has changed for children in Yemen since the Stockholm agreement on 13 December 2018. Every day since, eight children have been killed or injured. Most of the children killed were playing outdoors with their friends or were on their way to or from school.

“Mind-boggling violence over the past four years, high levels of poverty; and decades of conflicts, neglect and deprivation are putting a heavy strain on Yemeni society, tearing apart its social fabric – fundamental for any society and especially for children.”

Jan Egeland, secretary general of the Norwegian Refugee Council, said: “Yemenis need much more than just money. They need an end to interference in aid delivery, a lifting of the blockade, all ports and airports reopened, public services restored, and a nationwide ceasefire so that talks can bring an end to the conflict.”

Yemen’s prime minister Maeen Abdulmalik Saeed said on Monday that his government was appealing to the international community for support in achieving a just and comprehensive peace.

“The war in Yemen will not end until the Houthis are defeated, we hope that the humanitarian agencies will deal impartially with the situation in the country,” Saeed said during a meeting in Geneva ahead of the donor conference.