By Kwasi Kpodo
ACCRA (Reuters) - The outcome of Ghana's presidential run-off is too close to call and will be decided by voting on Friday in a single constituency where balloting has yet to take place, the electoral commission said on Tuesday.
In a twist to what was already a tense and closely fought race, the commission said the outstanding vote in the Tain constituency would determine the final result of the election in the West African state, the world's No. 2 producer of cocoa.
With votes counted from 229 of the 230 constituencies, John Atta Mills of the opposition National Democratic Congress (NDC) held a slender lead with 50.13 per cent of the votes, while Nana Akufo-Addo of the New Patriotic Party (NPP) had 49.87 percent.
Only 23,050 votes separated the two.
This made the race too close to call in the absence of Tain, which has around 53,000 registered electors and where voting did not take place in Sunday's run-off "due to circumstances beyond our control," election commission chief Kwadwo Afari-Gyan said.
"The results are so close that the outcome of the Tain constituency election could affect the eventual winner," Gyan said, adding the constituency, located in Ghana's central Brong Ahafo region, would vote on Friday.
Mills' supporters, who had already been celebrating his expected narrow victory, sang and danced around the commission headquarters, which was heavily guarded by police.
They remained confident, pointing out that in the inconclusive December 7 first round of voting, Mills' NDC had won Tain with a majority of around 2,000 votes.
"I'm not disappointed at all, I'm happy, because Mills is already a president and the whole of Ghana knows it. Tain is our territory and we are going to win there massively to make it a done deal," said NDC supporter, Kwako Assem, a taxi driver.
Ghana, on Africa's Gulf of Guinea, has enjoyed growth and stability in recent years, becoming an investors' favourite. The country, also a gold producer, will start producing oil in 2010.
POLARISING VOTE
Tuesday's announcement followed a tense wait at the commission, where thousands of Mills' supporters had gathered shouting "Change, change."
Gyan earlier met party and religious leaders to call for calm. Some banks and shops closed, fearing violence.
"These elections have really polarised us," NDC spokeswoman Hannah Tetteh said, adding Mills pledged to unite the nation if he won on Friday.
Armed soldiers and police, with water cannon and an armoured personnel carrier, held back the NDC supporters. Police fired shots into the air late on Monday to try to disperse them.
Akufo-Addo's NPP, which is also the party of outgoing President John Kufuor, complained of irregularities in results from some regions and said it would challenge them.
There were some reports of disorder in Sunday's vote. Many hoped Ghana's election could help salvage the battered image of constitutional democracy in Africa, tarnished by flawed elections in Kenya and Zimbabwe and military coups in Mauritania in August and in Guinea last week.
Observers from the European Union, the U.S.-based Carter Centre and the West African regional bloc ECOWAS said the run-off vote had been generally orderly and transparent.
The Eurasia Group risk consultancy, in a note by Africa analyst Sebastian Spio-Garbrah, predicted that Mills would be a "narrow electoral winner without a strong governing mandate."
Political analysts say the new president -- whoever he is -- will take over at a time when economic growth is expected to slow in the global downturn. He will have to deal with a growing budget and current account deficit, high inflation and unemployment and falling remittance and aid levels, they say.
Presidential rivals Mills and Akufo-Addo are both foreign-trained lawyers and both are aged 64.
(Writing by Pascal Fletcher)