U.S. Secretary of State John Kerry says Washington has "enormous concerns" for the restoration of the credibility of the elections process in Afghanistan.
Speaking on a visit to Beijing, he told reporters both of Afghanistan's rival presidential candidates must show statesmanship and leadership at a critical time.
He said the United States hoped "very much" over the course of the next few days that a way forward can be found and said Afghan candidates should not raise expectations among their supporters.
Presidential candidates Abdullah Abdullah and Ashraf Ghani have both claimed victory in the presidential runoff race.
Abdullah said initial results released on July 7 showing Ghani with a wide lead were plagued by fraud.
Ghani says the initial results are credible.
Kerry is due to meet with both candidates in Kabul on July 11.
Based on reporting by Reuters and AFP