Although the vote should have been held May 22, according to the constitution, the delay was not unexpected. The election commission has the authority to change the date of the presidential poll if anything should call into question the legitimacy of the vote.
The commission said security was a factor, along with a lack of trained staff, incomplete voter registration and weather concerns.
Afghanistan is experiencing its worst violence in the eight years since the U.S.-led invasion toppled the Taliban regime, which had been sheltering the al-Qaida network that perpetrated the Sept. 11, 2001, terrorist attacks.
About 70,000 foreign troops under NATO and U.S. command are helping the country tamp down an increasingly violent Taliban insurgency, particularly in the South, reported the Agence France-Presse.
"The international forces have expressed their readiness to send more troops in the course of the elections process to ensure better security," the Afghan election commission said in a statement, according to the AFP.
U.S. President Barack Obama has considered nearly doubling the U.S. force in Afghanistan from 36,000 to more than 60,000 over the next 18 months.
Defense Secretary Robert Gates told Congress Tuesday that the troop increase could happen by the summer.
Afghan forces also are gearing up to provide security for voters, but the election commission said the later date would give all security institutions more time to prepare.
NATO applauded the decision to set the vote for August. "We have always said it is important that elections should be held this year and we are pleased that the decision has now been taken," said NATO spokesman James Appathurai, quoted Reuters.
Hamid Karzai was elected president in December 2004 in a largely peaceful vote. The country expects to hold parliamentary elections in 2010.