KABUL (AFP) - Afghan presidential candidate Abdullah Abdullah has agreed to rejoin an audit of the votes, United Nations officials said on Sunday, after tense negotiations to keep the election on track amid a prolonged dispute over alleged fraud.

Mr Abdullah's team "has informed the United Nations that it will... resume its participation in the audit process tomorrow", the UN said in a statement.

Earlier on Sunday, the audit had restarted in Kabul without Mr Abdullah's observers, who refused to attend due to disagreements over how votes would be judged as fraudulent.

The country's first democratic transfer of power has been engulfed in a crisis over alleged fraud, undermining hopes that the election would be a key achievement of the US-led military and civilian aid effort since 2001. Instead, the battle between Mr Abdullah, a former anti-Taleban resistance fighter, and Mr Ashraf Ghani, an ex-World Bank economist, has threatened to spark a spiral of instability as NATO troops pull out and violence increases nationwide.