US President Barack Obama has called the deadly explosions that ripped through two restaurants in the Ugandan capital Kampala "deplorable and cowardly," a spokesman said.
"The president is deeply saddened by the loss of life resulting from these deplorable and cowardly attacks, and sends his condolences to the people of Uganda and the loved ones of those who have been killed or injured," National Security Council spokesman Mike Hammer said in a statement.
"The United States is ready to provide any assistance requested by the Ugandan government."
A senior administration official said the United States was in contact with its embassy in Kampala and was in touch with the Federal Bureau of Investigation regarding requests for assistance from Uganda's government.
At least 23 people were killed in the explosions as crowds watched the World Cup football final, police said.
One American national was among those killed, a US embassy spokeswoman in Kampala told AFP.
"At this time we can confirm that one American has been killed," said Joann Lockard. "I have no further information about American citizens."
An AFP correspondent saw three wounded US citizens at Kampala's main Mulago hospital where dozens other injured people had been taken for treatment.
One blast hit an Ethiopian restaurant in the south of the capital and the other was at a rugby sports club in the east of Kampala, police chief Kale Kayihura told reporters.
"These bombs were definitely targeting World Cup crowds," Kayihura said.
US Secretary of State Hillary Clinton sent her condolences to the families and friends of the victims in the United States and Uganda.
"At this tragic moment, the United States stands with Uganda," Clinton said in a statement. "We have a long-standing, close friendship with the people and government of Uganda and will work with them to bring the perpetrators of this crime to justice."
