Kerry during a joint press conference with two presidential runners late Saturday announced that all ballots cast during June 14 runoff polls will be audited.
The two runners Ashraf Ghani Ahmadzai and Abdullah Abdullah have reached an agreement to audit all votes and form a unity government.
The final numbers of the elections will be declared on July 22
Preliminary results announced by Afghanistan's election officials secured Ghani 56.44 percent and Abdullah garnered 43.56 percent of votes in the presidential runoff.
Both candidates alleged fraud in the election.
Votes are being re-counted at more than 7,000 polling stations.
The final official numbers will be declared July 22.
Hamid Karzai is stepping down after more than 10 years as the Afghan president.