Follow the latest news from the Sudan crisis here
US citizens should leave Sudan in the next 24 to 48 hours because fighting could escalate, White House representative Karine Jean-Pierre has said.
The administration was deeply concerned about the frequent ceasefire breaches on Wednesday, Ms Jean-Pierre said.
"The situation could deteriorate at any moment," she told a news briefing. "We are working continuously to create options for American citizens to leave Sudan."
Ms Jean-Pierre spoke shortly before Sudan's Rapid Support Forces paramilitary force agreed to extend a truce for 72 hours after battles with Sudan's army in Khartoum on Thursday.
Hundreds of people have been killed in almost two weeks of conflict between the army and the RSF, the two groups locked in a power struggle that threatens to destabilise the wider region.
The conflict has turned residential areas into war zones and sent tens of thousands of people fleeing for their lives.
Early on Friday, 52 evacuees from 12 countries arrived in Jeddah onboard Al Jubail, a Royal Saudi Navy vessel.
A day earlier, Saudi Arabia said 200 people arrived aboard the HMS Al Riyadh, representing The Gambia, Nigeria, Pakistan, Canada, Bahrain, Thailand, the US, Lebanon, Afghanistan, Palestine and Egypt.
The White House said the US had sent intelligence, surveillance and reconnaissance assets to support air and land evacuation routes that the Americans are using.
The US is also moving naval assets within the region, positioning them to provide any necessary support along the Sudanese coast, Ms Jean-Pierre added.
"This is a dynamic environment, and any option entails a degree of risk. But because the situation is unlikely to improve, we encourage Americans who want to leave to take advantage of the options that are available to them in the next 24 to 48 hours."
Several countries have evacuated citizens by air, while some have gone via Port Sudan on the Red Sea, about 800km by road from Khartoum.
Egypt has repatriated 5,327 of its citizens, 2,648 of whom were moved on Thursday.
In a separate statement on Thursday, the Egyptian Foreign Ministry said about 16,000 people had crossed from Sudan to Egypt, including 14,000 Sudanese citizens.
The French government said on Thursday it had rescued 936 people from Sudan.
The foreign ministry said those evacuated included not only French nationals but also citizens of the UK, the US, Canada, Ethiopia, the Netherlands, Italy and Sweden.
The UN secretary general thanked France for its "vital assistance in transporting 400 UN personnel and their dependents out of Sudan.
The French navy carried 350 people from Port Sudan to Jeddah, Saudi Arabia, on Tuesday night, while more than 70 were flown aboard a French Air Force transport plane to N'Djamena in Chad from El Fasher in Sudan on Thursday.
The UK said it had begun a "large-scale" evacuation of its citizens on Tuesday, with priority given to families with children, the elderly and the infirm.
Its first evacuation flight left and two more were expected overnight.
It had evacuated 897 people on eight UK flights as of 1500 GMT on Thursday with more flights to come.
The government estimates there are about 4,000 UK citizens in Sudan. It rescued British diplomats and their families on Saturday.
