The US President has said the fighting in Sudan "must end" and authorised potential new sanctions against those responsible for the bloodshed.
"The violence taking place in Sudan is a tragedy - and it is a betrayal of the Sudanese people's clear demand for civilian government and a transition to democracy," Joe Biden said in a statement.
"It must end."
Clashes between rival factions began on 15 April and have killed an estimated 700 people, mostly in Khartoum and Darfur, according to the Armed Conflict Location and Event Data Project.
The chaos has sparked a large-scale exodus of foreign citizens conducted by the militaries of several countries.
President Biden said the bloodshed, "which has already stolen the lives of hundreds of civilians and began during the holy month of Ramadan, is unconscionable."
The United States joins "the peace-loving people of Sudan and leaders around the world in calling for a durable ceasefire between the belligerent parties."
Mr Biden also signed an executive order that broadens authority to impose sanctions on those responsible, although it does not name potential targets.
In his statement, the president said those facing the sanctions are "individuals responsible for threatening the peace, security, and stability of Sudan; undermining Sudan's democratic transition; using violence against civilians; or committing serious human rights abuses."
Earlier, the United Nations pressed Sudan's factions to guarantee safe passage of humanitarian aid after six trucks were looted and air strikes in the capital undermined a supposed truce.
UN aid chief Martin Griffiths said he hoped to have face-to-face meetings with the warring parties within days to secure guarantees from them for aid convoys to deliver relief supplies.
The meeting could take place in the capital Khartoum, or another location, Mr Griffiths said from Jeddah, Saudi Arabia, following a visit to Port Sudan intended to plan a large-scale relief operation.
"It's important to me that we meet physically, face-to-face to discuss this, because we need it to be a public, accountable moment," he said.
The UN has warned the fighting between the army and the paramilitary Rapid Support Forces (RSF) risks causing a humanitarian catastrophe that could spill into other countries.
Air strikes were heard in Khartoum and the adjoining cities of Omdurman and Bahri, even as the two sides had agreed to extend a series of shaky and broken truces for a further seven days from today.
In Khartoum, millions are still trying to shelter from open warfare between an army using air strikes and heavy artillery and RSF forces embedded in residential neighbourhoods.
Most hospitals are not functioning and many areas are without power and water as supplies of food and fuel dwindled.
With international mediators pressing for peace talks, Sudan's army said it would send an envoy for talks with South Sudan, Kenyan and Djibouti leaders.
Aid has been held up in the nation of 46 million people where about one-third had already relied on relief assistance.
Speaking earlier, Mr Griffiths said he had been told by the UN's World Food Programme that six of its trucks travelling to the western region of Darfur had been looted en route, despite assurances of safety and security.
He spoke by phone to army leader Abdel Fattah al-Burhan and RSF commander Mohamed Hamdan Dagalo, commonly known as Hemedti, to tell them that specific aid corridors and airlift operations were required.
"We are very clear now in our operational requirements as to what we need in terms of commitments from them," he added.
In Nairobi, UN Secretary-General Antonio Guterres said the international community must tell the two leaders the situation is unacceptable.
The generals must face pressure to stop fighting, begin dialogue and allow a transition to civilian government, he said.
Mr Burhan's envoy, Dafallah Alhaj, said in Cairo that the army accepted talks but there would be no face-to-face discussions with the RSF and communication would be through mediators.
South Sudan said both sides have agreed to the ceasefire and to send representatives to talks.
Mr Hemedti said in a tweet that he was committed to "opening and securing safe corridors."
RSF later in a post on Facebook claimed its forces "still control 90% of the three cities of Khartoum" and said it affirmed a "full commitment to the declared humanitarian truce".
About 100,000 people have fled Sudan with little food or water to neighbouring countries, the UN says.
The conflict has spread to Darfur where the RSF emerged from tribal militias that fought beside government forces to crush rebels in a war dating back 20 years.
The army and RSF joined forces in a coup two years ago and had shared power as part of an internationally backed transition towards free elections and civilian government.
