"We fulfill our commitment to help the new state of South Sudan in its first steps, because we want it to succeed, and because its success will be our success,"Sudan's President Omar al- Bashir said in a conciliatory speech to tens of thousands of southerners at the official independence ceremony in Juba.
Khartoum announced its formal recognition of the world's newest nation, its former civil war enemy, on Friday, becoming one of the first countries to do so.
The 2005 peace agreement that ended the devastating 22-year conflict between the northern government and the former southern rebels paved the way for an independence referendum in January, in which the south voted almost unanimously to secede.
Since the referendum, the two sides have failed to agree on a number of key outstanding issues, such as how to manage the country's oil, most of which lies in the south, demarcation of their contested common borders, and the future status of the disputed Abyei region.
On Saturday, Bashir called for peace and stability, and positive brotherly relations based on mutual benefits. "It is our joint responsibility to go on building confidence to complete the agreement about the pending issues," he said.
He called on the international community and the European Union to fulfill their commitment to the Sudanese people, which they pledged when the 2005 north-south peace accord was signed.
"I'm also calling for US President Barack Obama to fulfill his commitment to remove sanctions from Sudan," he added.
North Sudan is facing an economic crisis, accentuated by the separation of the south, from which some three-quarters of the country's oil is pumped.
To ease the severity of its plight, Khartoum is desperately seeking the removal of US sanctions, first imposed in 1996, as a reward for its cooperation over the referendum and for allowing the smooth secession of the south.