A bomb blast exploded outside the main U.S. base in Afghanistan on Wednesday, wounding several people, a U.S. official said. An Afghan governor blamed the attack on a suicide car bomber, and the Taliban claimed responsibility.

The blast outside the main base at Bagram did not appear to kill anyone, according to early reports, said Capt. Elizabeth Mathias, a U.S. spokeswoman.

The governor of Parwan province, Abdul Jabar Takwa, said the bomber was in a car that exploded after he drove past a police checkpoint. Bagram is in Parwan province.

Takwa said that the bomber died in the blast, but he did not have any other casualty reports.

A Canadian general, meanwhile, said a roadside blast killed three Canadian soldiers in the south.

In the capital, Afghanistan's election commission announced that the presidential election should be held Aug. 20, rejecting a request from President Hamid Karzai to move the vote to the spring.

The commission — which said in January that the vote would be held in August — said the election couldn't be held earlier because of bad spring weather, a lack of money, security issues and logistical problems like the distribution of ballots.

Karzai last week asked the commission to re-examine the election date to see if it could be held in line with the Afghan constitution, which says Karzai must step down on May 22 and that elections must be held 30 to 60 days before that.

An August election likely presents the country with a constitutional crisis, because many Karzai foes have demanded that he step down in May and that a caretaker government be appointed until the late summer vote.