Hawa Alam Nuristani, chairwoman of the Independent Election Commission, made the announcement at a press conference on December 22 in the capital, Kabul.
Results for the September 28 presidential poll have been repeatedly delayed amid accusations of misconduct and technical problems with counting ballots.
Ghani’s main challenger, Chief Executive Abdullah Abdullah, won 39.5 percent of the vote, Nuristani said, adding that the results can still be challenged.
Abdullah agreed earlier in December to allow a ballot recount in provinces where his supporters had stopped the process for more than a month.
Afghan election officials had tried to launch a ballot recount in November but Abdullah halted the attempt, saying he wouldn’t let his observers participate.
Thousands of Abdullah’s supporters rallied in November in the capital against what they said was the presence of faked ballots amid a controversial recount that seemed set to favor Ghani.
If no candidate had obtained more than 50 percent of the vote, a runoff would have had to be organized.
If the preliminary results hold and Ghani remains president, it will give him the authority he has been seeking to demand a leading role in peace talks with the Taliban.
Until now, he and his government have been sidelined over the last year of direct talks between the United States and the Taliban.