Aid agencies have been struggling to access those in need amid funding shortfalls. The sum raised will go towards the overall target of $1.8bn the UN says is needed to help millions facing starvation.

While President Salva Kiir and his former deputy turned rival, Riek Machar, recently recommitted to allowing aid to reach the starving, the World Food Programme has seen no tangible improvement on the ground, according to its regional spokeswoman, Challiss McDonough.

The success of the relief operation hinges on an end to the clashes, which resumed on 11 May, just hours after a ceasefire pact signed by the two leaders came into effect. As usual, each side blamed the other for the violence.

The international community is bankrolling negotiations in Ethiopia’s capital, Addis Ababa, to try to fashion a political solution to what has become a brutal ethnic conflict. The key questions at the talks are whether Kiir and his allies are committed to the radical change demanded by the latest peace deal, and whether fighting will ease enough to allow serious negotiations. So far, there has been little indication of either.

Last week, rebels said government attacks in Upper Nile and Jonglei threaten to return the world’s newest state to full-blown war. South Sudan’s military spokesman, Philip Aguer, said on Tuesday that Machar’s fighters were being armed and assisted by militias funded by Sudan’s government. There was little chance of a lasting ceasefire while insurgents were re-arming, mobilising and training with foreign support, he added. Analysts question Machar and Kiir’s control over local commanders.

The east African nations mediating the conflict have been receiving updates from their ceasefire monitors about the nature of the clashes, but a peacekeeping force to prevent future skirmishes has yet to be approved.

Although leaders in the region and beyond agree on the urgent need for a protection force, defining its mandate is proving tricky: the initiative must be a robust, African-led intervention force that is also funded and authorised by the UN.

Before talks adjourned for 12 days on Monday, and amid ongoing clashes, delegates in Addis Ababa were discussing how to implement the latest truce and what a transitional government could look like.

On security issues, Machar’s team have objected to the continued presence of Uganda’s military, which is allied with Kiir, according to Mabior Garang, a spokesman for the rebels. Mediators have outlined steps that need to be taken to make the truce work, but the parties have not signed up because of the Uganda dispute.

Garang said discussions on political reforms and the transition also took place last week. The parties have agreed that key leaders recently released by the government need to be included in the talks, which could involve a swath of South Sudanese civil society. Almost 100 people are scheduled to take part in the next round.

The mediation team, led by the former Ethiopian foreign minister Seyoum Mesfin, said talks have been a more inclusive, representative and forward-looking process since Kiir and Machar signed the truce, but the current sticking points of Uganda and who should sit round the table have hindered the process since it began in December.

The broader question of the sincerity of Kiir’s administration also lingers. Although the government has agreed to be dismantled, it still presents itself as legitimate and intact. In a typically bullish display, the information minister, Michael Makuei, said Kiir’s administration had a duty to take back rebel-held territory seized since the first truce on 23 January, in order to protect civilians.

Last week, in Nairobi, Makuei reportedly blamed the US for backing rebels as it seeks to replace a democratically elected government that is too friendly with China.

Ethiopia, a key and even-handed regional player, insists progress has been made and that Kiir understands the need for change. An official close to the talks says the president had suggested the phrase “transitional government of national unity” should be central to the 9 May deal. Others claim the Kiir’s understanding of the phrase was hazy and optimistic, and that he had been pressured to sign.

A leading Machar delegate says a chasm between the parties remains: his side is fighting to unseat a corrupt dictatorship that embarked on ethnic killing in response to a democratic challenge, while the government considers its opponents ragtag insurgents intent on causing mayhem. “It will be difficult to move forward unless we agree on the problem,” he says.