The United Nations in South Sudan was readying aid on Saturday for towns ravaged by conflict but was waiting to see if a new ceasefire deal holds between the president and rebel leader before sending it.
South Sudan President Salva Kiir and rebel commander Riek Machar signed the deal on Friday after growing international pressure to end the ethnic fighting that has raised fears of genocide. A January accord collapsed swiftly after being agreed.
African mediators, the United States and other Western nations had pushed for face-to face talks as fierce fighting increasingly pitted Kirr's Dinka people against the Nuer of Machar. The United Nations reported targeted ethnic killings.
"An end to the violence will allow people some breathing space, to move around more safely and to plant and take better care of themselves in the coming months," Toby Lanzer, the UN humanitarian coordinator in South Sudan, said in a statement.
He said the United Nations was standing by in the capital Juba "to load barges with life-saving aid and transport it to key destinations such as Bentiu and Malakal".
Some of the fiercest fighting was in and around Bentiu and Malakal, both capitals of oil-producing regions.
UN officials said there were no immediate reports of any fighting on Saturday - though news of clashes in remote areas can take a long time to emerge.
Rebel spokesman Lul Ruai Koang, speaking on Saturday morning, said he also had no reports of clashes, adding: "We are optimistic, but we cannot guarantee the government side."
A UN humanitarian office official said supplies would be sent when it was clear the two sides were sticking to the pact that was due to take effect within 24 hours of Friday's signing.
The conflict has killed thousands of people and driven about a million from their homes. Some fled into neighbouring states. US secretary of state John Kerry and UN secretary general Ban Ki-moon both visited the Texas-sized country this month, part of a diplomatic push by regional and world leaders still haunted by Rwanda's 1994 genocide.
"Civilians were not only caught up in the violence, they were directly targeted, often along ethnic lines," the United Nations said in a report shortly before the deal was reached.
The UN mission in South Sudan, UNMISS, called for further investigations into possible crimes against humanity, including extrajudicial killings, enforced disappearances, rape, arbitrary arrests and other reported abuses.