Sudan's parliament has approved a controversial bill paving the way for a referendum on possible independence for the country's oil-producing south.
MPs passed the bill on Tuesday, despite opposition from southern Sudanese legislators over a clause that would allow southerners living outside South Sudan to cast absentee ballots.
"Finally, after a long journey, we approved this law," Ahmed Ibrahim al-Tahir, the parliament's chairman and member of north Sudan's National Congress Party (NCP), said.
However, parliamentarians from the Sudan Peoples' Liberation Movement (SPLM), the south's main party, had walked out of the session in protest.
The SPLM is concerned that southern Sudanese now living in the north could be less supportive of a campaign for independence.
Despite their opposition, the approval of the bill marked the end of months of political wrangling between the two parties over the terms of the law.
South Sudan secured the independence vote as part of a 2005 peace accord that ended decades of civil war that saw the deaths of millions of people.
Analysts had warned of a risk of a return to conflict if the parties could not agree terms for the laws, supposed to pave the way to elections, due in April 2010, and the referendum on southern independence in 2011.
The national vote will be the first in Sudan since 1986, three years before al-Bashir toppled a democratically elected government in a bloodless military coup.
Relations between the SPLM and the NCP of Omar Hasan al-Bashir, Sudan's president, have been strained, most recently when authorities in Khartoum arrested two senior SPLM officials and scores of their supporters during a protest earlier this month.