Kabul ? Both main candidates for Afghan president claimed to be ahead Friday after an election marred by violence, spotty turnout and fraud allegations — threatening U.S. hopes for Afghans to come together to combat the challenges of Taliban insurgency, corruption and poverty.

President Hamid Karzai’s campaign insisted he would have enough votes to avoid a runoff with his chief challenger, Abdullah Abdullah, a former foreign minister. Abdullah countered that he was leading but suspected there would be a runoff.

Election officials called on the candidates to refrain from such claims, which could delay formation of a new government. Officials of Afghan and international monitoring teams agreed that it was too early to say who won or to know whether fraud was extensive enough to influence the outcome.

Millions of Afghans voted Thursday in the country’s second-ever direct presidential election, although Taliban threats held down the turnout, especially in the militant south where Karzai was expected to run strong among his fellow Pashtuns. Insurgent attacks claimed more than two dozen lives.

Partial preliminary results won’t be released by the election commission before Tuesday with final official returns due in early September. Officials count ballots at voting centers around the country and then send the figures to Kabul, where they are tabulated, verified and announced.

Nevertheless, the absence of official figures didn’t dissuade supporters of the two leading candidates from issuing their own claims, which they said were based on reports from their representatives at the counting centers.

Karzai’s campaign spokesman, Waheed Omar, said the president’s campaign believes “we are well ahead” in the ballot count and will end up with more than 50 percent of the votes — enough to avoid a runoff that Omar said would be “logistically, financially and also politically” problematic.

“Our prediction is that the election will not go to the second round,” Omar said. “Our initial information is that we will hopefully be able to win the elections in the first round.”

Abdullah challenged the claim, telling The Associated Press that he was in the lead “despite the rigging which has taken place in some parts of the country.”

The U.S. Embassy and Afghanistan’s Independent Election Commission dismissed both sides’ claims, saying it was too early for anyone to declare victory.