The deadline for a vote on whether Sudan, Africa's largest country, should split in two is now less than a fortnight away.
Voters in Southern Sudan are being asked to decide whether the region, which is rich in oil, should secede from Sudan. Voting will be held on 9 January.
The referendum is part of a peace accord to end a civil war that killed more than two million people.
Under the accord, Southern Sudan achieved a measure of independence from Sudan five years ago.
Former rebel Salva Kiir of the Anya-Nya (Snake Venom) army now heads Southern Sudan's autonomous government.
The ABC reports the president warns that the South refuses to be provoked.
"We have been very courteous and we have been very patient to move along with our partners, whatever provocations they have done, you all know," he said.
"But we refuse to be provoked and this is why we have reached this stage today."
Earlier this month, ballot papers were distributed to the Southern Sudan, removing at least one uncertainty about whether the ballot would go ahead.
But Mr Kiir has warned there are elements determined to block the ballot.
"The enemies of peace are not sleeping. They are working day and night to make sure the referendum does not take place," he said.
"People are talking about unity all the time but I think it has now become very clear to the unionists that unity may not be possible."
Wider implications
The ABC reports any return to conflict could have serious consequences for Sudan's neighbours.
Sudan lies astride the middle reaches of the Nile, the primary source of water for Egypt.
Libya and Egypt are concerned about refugees flooding over their borders as a result of renewed fighting.
There are reports the UN is planning for the possibility that almost three million people would be displaced if fighting broke out once more.
