Washington - The United States on Monday condemned a Sudanese air raid on South Sudan and urged an "immediate" halt to hostilities and a return to talks, the State Department said.
"The United States strongly condemns Sudan's military incursion into South Sudan yesterday and calls for the immediate cessation of hostilities and the withdrawal of all Sudanese armed militia from South Sudan," said spokesperson Victoria Nuland in a statement.
"Sudan must immediately halt the aerial and artillery bombardment in South Sudan by the Sudan Armed Forces. Sudan and South Sudan must end all military support for rebel groups within the other country," she added.
Sudanese bombs fell on Monday on a key bridge and a market in the state capital of Bentiu, killing at least two children, prompted heavy gunfire from Southern soldiers hoping to shoot down Khartoum's warplanes.
Nuland said Washington recognised South Sudan's right to self-defence and urged it to exercise restraint in its reaction to Sudan's attack in Unity State, "and to refrain from disproportionate actions which would only further enflame the hostilities between the parties."
Both governments must agree to an "immediate unconditional cessation of hostilities" and recommit to talks, Nuland said.
President Barack Obama on Friday in a videotaped message to the people of the two countries called for an end to fighting and negotiations between the leaders of the two countries to settle their conflict.
Border clashes between Sudan and South Sudan have escalated with waves of air strikes hitting the South, and Juba seizing the Heglig oil hub on April 10.
Since the invasion, production at Heglig has been shut and facilities there are leaking. Each side accused the other of damaging the oil infrastructure.
The Heglig violence was the worst since South Sudan won independence in July after a 1983-2005 civil war in which some two million people died.
Tensions have gradually mounted over the disputed border and other unresolved issues.
South Sudan broke away from the north following a referendum under a 2005 peace deal that ended a two-decade civil war in which more than two million people died.