The United States expects the fighting between two military chiefs in Sudan to continue as neither has an incentive to seek peace, US Director of National Intelligence Avril Haines has said.

“The fighting in Sudan between the Sudanese Armed Forces and the Rapid Support Forces (RSF) is, we assess, likely to be protracted as both sides believe that they can win militarily and have few incentives to come to the negotiating table,” Haines told a US Senate hearing on Thursday.

“Both sides are seeking external sources of support, which, if successful, is likely to intensify the conflict and create a greater potential for spillover challenges in the region,” she said.

Haines, the top US intelligence official, said the fighting has exacerbated already-dire humanitarian conditions, “raising the spectre of massive refugee flows and aid needs in the region”.

Fighting continued in Khartoum for the 20th straight day Thursday after the latest ceasefire between the two sides failed. Fierce fighting could be heard in central Khartoum as the army tried to push back the RSF from areas around the presidential palace and army headquarters.

Each side appears to be battling for control of territory in the capital ahead of any possible negotiations, though the leaders of both factions have shown little public willingness to hold talks after more than two weeks of fighting.

Reporting from Khartoum, Al Jazeera’s Hiba Morgan said some of the fighting was concentrated around the presidential palace on Thursday.

“Fighter jets were flying overhead around the vicinity of the presidential palace and the general command of the army headquarters. There were heavy artillery being fired around the presidential palace,” she said.

“We can see plumes of smoke rising at the general command of the army. The general command is under the control of the military, but many areas around it are under the control of the Rapid Support Forces including the presidential palace, which since Wednesday the Sudanese army has been trying to regain control of. People say they were not able to leave their homes because of the ongoing fighting.”

Heavy bombardments also rang out in the adjoining cities of Omdurman and Bahri. Both sides had agreed to a seven-day ceasefire, which has been violated.

“Since yesterday evening, and this morning, there are air strikes and the sounds of clashes,” Al-Sadiq Ahmed, a 49-year-old engineer speaking to Reuters from Khartoum, said.

“We’ve got into a state of permanent terror because the battles are around the centres of residential neighbourhoods. We don’t know when this nightmare and the fear will end,” he said.

The United Nations, meanwhile, pressed the warring factions to guarantee safe passage of aid after six trucks were looted. UN aid chief Martin Griffiths said he hoped to have face-to-face meetings with both sides within two to three days to secure guarantees from them for aid convoys.

The UN has warned that fighting between the army and RSF, which erupted on April 15, risks causing a humanitarian catastrophe that could spill into other countries. The UN High Commissioner for Refugees (UNHCR) said it was preparing for an outflow of 860,000 people from the North African country, adding $445m would be needed to support them just through October.

“We urgently need timely, new funding to respond to the mounting needs,” said Raouf Mazou, the UNHCR’s assistant chief of operations.

“The needs are vast, and the challenges are numerous. If the crisis continues, peace and stability across the region could be at stake,” Mazou added.

Sudan said on Tuesday that 550 people had died and 4,926 people been wounded so far in the conflict.

About 100,000 people have fled Sudan with little food or water to neighbouring countries, according to the UN. (Al Jazeera)

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