Secretary of State Antony Blinken said on Thursday that the United States was working with Sudan's warring generals to extend an expiring, shaky ceasefire that he helped broker.
Blinken said he expected to say more "in the coming hours" on the situation in Sudan, where the army has renewed air strikes on rival paramilitaries in the capital Khartoum even before the truce expires at midnight (2200 GMT).
"We are very actively working to extend the ceasefire," Blinken told reporters.
"We've had a 72-hour ceasefire, which like most ceasefires is imperfect but nonetheless has reduced violence. And that's obviously created somewhat better conditions for people in Sudan," he said.
Blinken said that the United States was also working to establish a more regular route for the departure of foreigners from Sudan.
Meanwhile, more than 3,500 people have arrived in Ethiopia after fleeing the continuous fighting in Sudan, an official from the UN's International Organization for Migration told AFP.
Many of the arrivals are Turkish nationals, according to the agency.
The United Nations has issued a warning that the violence could force as many as 270,000 people to seek refuge in neighbouring South Sudan and Chad, while others have fled to Egypt and Ethiopia.
"Between April 21 and April 25, more than 3,500 arrivals have been recorded from over 35 nationalities," Eric Mazango, communications officer for the IOM in Ethiopia, told AFP in an email received Thursday.
The fighting between rival Sudanese troops and paramilitaries has now entered its 13th day, with over 500 people killed, while civilians are suffering from severe shortages of basic needs including water, food and fuel.
Earlier today, the Sudanese army pounded paramilitaries in the capital Khartoum with air strikes while deadly fighting flared in Darfur as the conflict entered a 13th day despite a US-brokered ceasefire.
Late Wednesday, the army said it had agreed to talks in Juba, capital of neighbouring South Sudan, on extending the three-day truce which expires on Friday "at the initiative of IGAD", the East African regional bloc.
There have been multiple truce efforts since fighting broke out on 15 April between Sudan's regular army led by General Abdel Fattah al-Burhan and the paramilitary Rapid Support Forces (RSF) commanded by his deputy turned rival, Mohamed Hamdan Daglo. All have failed.
The fighting has continued despite the US-brokered ceasefire that took effect on Tuesday, with warplanes patrolling the skies over the capital's northern suburbs as fighters on the ground have exchanged artillery and heavy machine gun fire, witnesses said.
Burhan agreed on Wednesday to the IGAD proposal for talks on extending the truce by a further 72 hours, the army added.
The RSF's response to the proposal remains unclear, according to reports.
At least 512 people have been killed and 4,193 wounded in the fighting, according to health ministry figures, although the real death toll is likely to be much higher.