The White House says President Barack Obama has told Afghanistan's two presidential candidates that it is important to complete a power-sharing deal as soon as possible so the country can form a new government.
A White House statement said Obama spoke with both men on September 6.
A final agreement would help solidify international backing for Afghanistan and help stabilize the country.
Former Foreign Minister Abdullah Abdullah won the first round of voting in April but did not get enough votes to avoid a June runoff.
According to a preliminary count, former Finance Minister Ashraf Ghani Ahmadzai took the second round, but both sides have alleged election fraud.
The candidates are trying to negotiate a power-sharing agreement to settle the dispute and pave the way for a national unity government.