BUENOS AIRES: Polls indicate that if ruling party candidate Daniel Scioli wins Argentina's presidential election in the first round on Sunday it will be by a narrow margin, raising the prospect of a slow second count, two prominent pollsters said on Tuesday.

Nationwide surveys show Scioli, President Cristina Fernandez's chosen successor, straddling the 40 percent threshold that would be enough for him to win outright providing he has a lead of 10 points over his nearest rival.

"With the numbers we have, the truth is that none of the candidates are going to accept defeat at midnight," said Mariel Fornoni, director of consultancy Management & Fit.

Scioli's main rival is the centre-right mayor of Buenos Aires, Mauricio Macri. He promises to dismantle capital controls and trade restrictions from his first day in office to win investor confidence and bring hard currency into the dollar-starved economy.

Scioli talks of a more gradual approach to monetary reform while maintaining Fernandez's generous social welfare safety net.

On Sunday polling stations will count ballots and file their numbers to a central tallying centre to provide a provisional count. If Scioli does win outright by a slim margin his rivals may well await a final count before ceding victory.

While a provisional result is likely to be known by midnight, an official result could take between five and seven days, Argentina's electoral body says.

"It's going to be a complex count," said Ricardo Rouvier, a second pollster.

Argentina's electoral body is generally well respected and allegations of fraud in general elections are rare.

However, a disputed count that involved allegations of vote burning and prompted opposition protests, in a gubernatorial election in northern Tucuman province in August, raised questions about the integrity of Argentina's voting system.