Talks between rebels and the government to try to end seven months of bloodshed in South Sudan resumed in Ethiopia’s capital, Addis Ababa, on Monday. The session begins amid continuing reports of fighting and increasingly dire warnings from aid agencies of impending famine.

While the negotiations, mediated by a bloc of northeastern African nations called the Intergovernmental Authority on Development (Igad), produced an agreement in May to halt the fighting, clashes have continued – and there’s little sign that deep political differences are about to be resolved.

Civil war began in December when a long-standing dispute between President Salva Kiir and his former deputy, Riek Machar, descended into fighting between rival soldiers in the capital, Juba. Kiir arrested senior regime figures after accusing them of attempting a coup. Machar – who had previously announced his intention to challenge a president he said was increasingly autocratic – escaped an army assault on his house by the military, fled the capital and became the figurehead of a rebellion.

The conflict has killed thousands of people and displaced about 1.5 million, according to the UN. Up to 50,000 children face death in the next few months, with 7 million people at risk of hunger and disease, unless the humanitarian situation improves, the UN says. Aid agencies are warning of a famine.

The fighting has been marked by atrocities and has frequently featured clashes between the Dinka ethnic group of Kiir and Machar’s Nuer people. Many members of Nuer militias say they are avenging the killing of their brethren by Dinka soldiers in Juba in December.

A key idea being pushed by the Igad mediators – who are led by Ethiopia’s former foreign minister, Seyoum Mesfin – is for the warring sides and other parties to agree to the details of a transitional government of national unity. Similar compromise arrangements were applied under African pressure following electoral violence in Zimbabwe and Kenya.

Although Kiir has agreed to the concept, his camp has not indicated a willingness to concede power. The president said in June that it would not be appropriate for him to step down as he is the nation’s elected leader.

South Sudan, which gained independence from Sudan in 2011 after half a century of on-off rebellion against Khartoum, has not held its own general election. Kiir was voted into office when the country was still formally part of Sudan.

Machar, meanwhile, would welcome any significant change in the government. He has been pushing for a total revamp of the state, including the creation of a federal system.

The hope from the international community is that substantial discussions will now occur about implementing the agreed truce and how to reform key areas of the government, such as the military and financial management.

The danger is that talks once more get bogged down in procedural issues, and that more armed clashes create an atmosphere that is not conducive to progress. On 10 June, the parties agreed to finalise discussion on the details of the transitional government by 10 August, but talks adjourned on 23 June after rebels complained that civil society groups were not fairly represented. That issue of “inclusivity” has now been resolved – yet other hitches could easily emerge.

Clashes are still occurring, with the latest report of violence in Maban County in the north of the flashpoint oil-rich state of Upper Nile. Rebelssaid at the weekend that the government was positioning troops for “total war”, while at Monday’s opening ceremony of the peace talks, the head of the government delegation, ex-foreign minister Nhial Deng Nhial, said Machar’s insurgents, “frustrated” at their lack of military gains, would soon start attacking civilian targets.

Igad’s Seyoum and other international partners have once more warned South Sudan’s political elite they will not tolerate continued fighting and evasive approaches to the negotiations. Behind the stern words lies a threat of sanctions.

The US and EU have already slapped travel bans and frozen the assets of military leaders from both sides. Norway’s envoy to the region, Jens-Petter Kjemprud, on Monday said Igad, the African Union and the UN security council were discussing more punitive measures.

But one European diplomat believes Igad’s members are not close to agreeing interventions such as an arms embargo or a mechanism to manage South Sudan’s oil revenues.

Sudan and African partners have been critical of sanctions imposed on President Omar al-Bashir’s government, while there is a similar opposition to western interference in Kenya.

Uganda’s early and ongoing military intervention to prevent the downfall of Kiir’s government is also a point of contention among Igad states. While recognising Kiir’s formal legitimacy, other regional powers such as Ethiopia and Kenya have strived to not take sides. Unless Igad “gets its act together” and provides a lead it will be hard for the international community to act, the diplomat says.

It was hoped that the arrival of troops from Kenya, Rwanda and Ethiopia to discourage clashes and protect civilians would help compel the belligerents to concessions.

But an Ethiopian insider says that after the March announcement of the force, the promised rapid deployment has not occurred. Around 10 days ago, rebels and government loyalists battled for control of Nasir – a town only 30km from Ethiopia’s border – apparently without any international troops nearby to act as a deterrent.