Secretary of State Hillary Rodham Clinton is "strongly condemning" the explosions that killed more than 60 people, including at least one American, in Uganda on Sunday.
Clinton says the United States will work with the Ugandan government "to bring the perpetrators of this crime to justice."
Officials in Uganda's capital, Kampala, say 64 people died in simultaneous bombings of World Cup soccer viewing crowds.
Two blasts bearing the hallmarks of international terrorists ripped through crowds at a rugby club and a restaurant in Kampala. Several other Americans were among the wounded.
The deadliest attack occurred at the rugby club as people watched the game between Spain and the Netherlands on a large-screen TV outdoors. The second blast took place at an Ethiopian restaurant, where at least three Americans were wounded.
Kampala's police chief said he believed Somalia's most feared militant group, al-Shabab, could be responsible for the attack. Al-Shabab is known to have links with al-Qaida.