Despite allegations of voting fraud, Karzai said the poll was valid and noted that Afghanistan "lacks the proper administrative system the world has."
Karzai admitted there were irregularities in voting, but said it was in the interests of national unity to move forward now.
More than 650 ballot boxes were removed from the tabulation process due to suspicions they were stuffed with fake ballots.
Meanwhile, a car bomb exploded near a mosque in Zaranj, the capital of the southern Nimruz Province.
The bomb killed a deputy provincial police chief and one of his bodyguards.
In a separate incident an intelligence official was killed today in the eastern Kunar Province. The official was riding his bicycle home when a roadside bomb detonated.