Former World Bank official Ashraf Ghani is leading his rival, former foreign minister Abdullah Abdullah, in a presidential runoff that would mark Afghanistan’s first transfer of power through the ballot, according to preliminary results released Monday by election authorities.

The Independent Election Commission (IEC) announced that Ghani, an ethnic Pashtun, had secured 56 percent of the vote, while Abdullah, who is popular among the Tajik community, won 43 percent.

The tallies are not final, however, pending an official investigation of nearly 2,000 polling stations suspected of registering fraudulent ballots, the commission said. Also Monday, IEC Chairman Ahmad Yusuf Nuristani said both campaigns had agreed on four criteria proposed by the United Nations that would allow for a broader inspection encompassing 7,000 polling centers, or about 3 million votes.

Fazl Rahman Orya, a spokesman for the Abdullah campaign, said that it rejects the IEC’s figures and that any decision made by the commission “holds no credibility.” Abdullah has accused election officials of widespread vote-rigging in favor of Ghani, and he announced shortly after the June 14 runoff that he did not recognize the ballot-counting process as legitimate.

In announcing the initial tallies Monday, Nuristani conceded that government officials and police chiefs, responsible for securing polling stations, had engaged in fraud and tampered with the process. He did not provide details.

The Abdullah campaign had vehemently opposed the release of preliminary results that included fraudulent votes.

Monday’s announcement “might have some effect on public opinion, internationally and nationally, in that people will think: Whatever the voting system, whatever the fraud, Ghani is ahead,” said Aminullah Habibi, a former adviser to coalition forces in Afghanistan and a consultant to the Abdullah campaign. “And that might be something that is very difficult to reverse.”

In recent days, the two sides were engaged in heated negotiations over the possibility of a more comprehensive recount of ballots at polling centers where voting patterns appeared suspicious.

“We have made some progress, and there was a positive climate” between the two sides, a senior adviser to the Abdullah campaign, Mahmoud Saikal, said Monday.

But campaign officials would not say whether the talks with Ghani representatives would continue.

The Abdullah campaign was particularly critical of the IEC’s 8 million turnout figure, about 1.5 million more voters than in the first round. The Ghani camp has defended the number, claiming a more robust mobilization effort for the runoff.

“It’s a joke,” Habibi, the consultant, said of the number. “I wish it wasn’t.”

Ghani, a former finance minister, finished second to Abdullah in the first round of presidential voting, in April, but Abdullah did not attain a majority, necessitating the runoff.

In Washington, State Department spokeswoman Jen Psaki noted that the figures released Monday “are not final or authoritative” and could change based on the findings of Afghan electoral authorities. “Serious allegations of fraud have been raised and have yet to be adequately investigated,” Psaki cautioned in a statement.

She called on Afghan authorities to work with the United Nations to implement the proposed audits, which she said can be completed in time for the scheduled Aug. 2 inauguration of the new president if the process begins promptly.

“A full and thorough review of all reasonable allegations of irregularities is essential to ensure that the Afghan people have confidence in the integrity of the electoral process and that the new Afghan president is broadly accepted inside and outside Afghanistan,” Psaki said. Meanwhile, “neither candidate should claim victory” based on Monday’s IEC announcement, Psaki said.

“The United States does not support any individual candidate” but wants Afghanistan to have a president who can unite the country and “govern effectively,” Psaki said. She warned that continued U.S. support “requires that Afghanistan remains united and that the result of this election is deemed credible.”

Sayed Salahuddin and Mohammad Sharif contributed to this report.