Sean McCormack, the US state department spokesman, told reporters on Monday: "We would not say that it was a PR stunt.
"We have serious concerns any time anybody takes their own life."
Colleen Graffy, the deputy assistant secretary of state for public diplomacy, had said earlier that the deaths "certainly [are] a good PR move to draw attention".
And Navy Rear Admiral Harry Harris had said he believed that the suicides were an "act of asymmetric warfare against us" rather than an act of desperation.
The pair's comments prompted newspapers and rights groups to criticise the US for its continued detention without trial of hundreds of people it regards as terror suspects at the prison camp.
"Cold and odious"
Le Monde newspaper in France condemned Graffy's comments, saying that they "illustrate the gulf which separates American authorities from the rest of the world on this sinister question".
The Guardian newspaper in Britain called Harris's remarks "cold and odious".
"It is entirely in keeping with the clinical illegality of America's treatment of terror suspects since 2001," the newspaper said.
The three men - two Saudis and one Yemeni - hanged themselves after being held at the prison camp for about four years without charge.
About 460 men accused of links to Afghanistan's Taliban or the al-Qaeda network are still being held.
Most have been behind bars for more than four years without charge.
Amnesty International said Graffy's comment "shows a chilling disregard for human life" and said it was "deeply concerned" by Harris's remark.
Rob Freer, an Amnesty official, said: "The commander's statement is entirely inappropriate and is part of a pattern of official commentary on the presumed guilt of detainees who have never had an opportunity to challenge their detentions in a court of law."
The international Red Cross said it hoped to bring forward a scheduled visit to the camp because of the suicides of the inmates, but it said it was not an investigation.
The Paris-based International Federation for Human Rights said it was shocked by the American officials' statements, which it branded "shameful and revolting".
The Daily Mail newspaper, a right-wing British tabloid, said the officials had spoken "with utter insensitivity to world opinion" in an editorial headlined "From the high moral ground to the gutter."
El Mundo newspaper in Spain called the comments "gruesome".