More than 100,000 people have fled Sudan since heavy fighting broke out between rival forces on 15 April, the UN has said.
Officials warned of a “full-blown catastrophe” if fighting does not end.
A further 334,000 people have been displaced within Sudan.
Fighting is continuing in the capital, Khartoum, between the army and the paramilitary Rapid Support Forces (RSF), despite a ceasefire due to be in force.
Diplomatic efforts are being stepped up to try and get the warring parties to the negotiating table.
On Tuesday, South Sudan’s foreign ministry said the army and RSF had agreed “in principle” to a new seven-day truce from 4 May, and had promised to send representatives to talks.