Khartoum - The referendum on independence for Southern Sudan is a "ticking time bomb", US Secretary of State Hillary Clinton has said.

The vote is due in January and Mrs Clinton said the outcome was "inevitable" - backing for secession.

She called on Sudanese and international leaders to do more to prepare for the poll.

The referendum was part of a 2005 peace deal to end two decades of conflict between the north and oil-rich south.

Mrs Clinton observed that the north was unlikely to welcome the prospect of losing its share of oil revenues from the south but said the south's leaders must make "some accommodations" with the north "unless they want more years of warfare".

Southern Sudan, where most people are Christian or follow traditional religions, is already semi-autonomous and is run by the SPLA former rebels, who fought the Muslim-dominated, Arabic-speaking north until the 2005 deal.

US President Barack Obama is to attend a special UN meeting on Sudan's future on 24 September, his ambassador to the UN, Susan Rice, announced.

The Southern Sudanese authorities last month launched a competition to compose a new national anthem for the region.