The NATO force in Afghanistan says it had prior intelligence reports that militants were operating near a U.S. military base hit by a suicide bomber during a visit by U.S. Vice President Dick Cheney.
NATO spokesman Tom Collins said Wednesday recent intelligent suggested there was the threat of a bombing near the Bagram air base, about 60 kilometers from Kabul.
At least 22 people were killed when a suicide bomber blew himself up Tuesday among a group of Afghan workers outside the base. Military officials say 27 people were wounded in the attack.
Cheney was not hurt. He arrived back in Washington early this Wednesday morning.
The Taleban has claimed responsibility for the blast and said it was targeting Cheney.
Collins said it is unlikely the militant group knew Cheney was at the base, because his visit was unannounced. He stayed there Monday night after bad weather postponed his trip to Kabul.
After the explosion, the U.S. vice president said he was briefly moved to a bomb shelter.