|Sirleaf is a strong favourite for the run-off, having secured the backing of former rebel leader Prince Johnson[Reuters]
Liberia's election commission chief has resigned after accusations of bias in the recent presidential elections and just days before a planned presidential runoff.
"I chose to step down for the sake of Liberia and so that (challenger Winston Tubman's) CDC [Congress for Democratic Change] would not have an excuse not to participate in the run-off," James Fromayan told the Reuters news agency on Sunday.
Tubman last week threatened to withdraw from the November 8 run-off, the country's second post-war vote, unless there was a change of leadership at the election commission.
Fromayan, who has denied any wrong doing, said he would be replaced by Elizabeth Nelson, his deputy, but he said he did not know it would be a permanent arrangement.
There was no immediate reaction from Tubman's camp.
The first round of voting on October 11 saw incumbent President Ellen Johnson Sirleaf win 43.9 per cent of the vote while Tubman, her closest rival, won 32.7 per cent.
Sirleaf, who won this year's Nobel Peace Prize along with her compatriot Leymah Gbowee and Tawakul Karman of Yemen, is a strong favourite for the run-off, having secured the backing of a former rebel leader, Prince Johnson.
He came third in the poll with about 11.6 per cent.
Last week, there was confusion over whether the CDC would take part in the second round of voting. Party officials issued contradictory messages and Tubman accused the election body of not taking his complaints seriously.
George Solo, the CDC campaign manager, said one of the party's complaints was that ballot papers had been pre-marked.
"We presented photos of ballot boxes which had been tampered with by NEC employees," he told the AFP news agency.
"We also have the issue of tally sheets scratched out and their numbers changed. Old people wanted to vote for certain people but NEC workers were not ... assisting them.
"The ink which was used was not an instant dry which made lots of votes invalid. These are all things that should have been done differently and properly."
The fraud accusations raised tensions in the country which was devastated by a 14-year civil war, which ended in 2003, leaving about 250,000 people dead.
The election was marred by violence with the office of Unity Party and that of a radio station seen as pro-opposition torched after preliminary results showed Sirleaf was leading.
The UN Security Council stressed on Wednesday council "the importance of peaceful, credible and transparent elections" and encouraged Liberian and international groups to deploy as many observers as possible to monitor the second round of voting.
About 800 foreign monitors and 4,000 local observers were on the ground for the first round, largely praising the smooth and peaceful conduct of the poll.