The four-day standoff appeared to end Saturday after Algerian special forces stormed the complex. The clash left at least 23 hostages dead and killed all 32 militants involved, the Algerian government said.
The State Department issued a travel warning Saturday night for Americans in or traveling to Algeria, citing credible threats of the kidnapping of Western nationals. The department also authorized the departure from Algeria of staff members' families if they choose to leave.
In a statement from the White House, Obama said the blame lay with the militants and that the United States condemns their actions.
"This attack is another reminder of the threat posed by al-Qaida and other violent extremist groups in North Africa," Obama said. "In the coming days, we will remain in close touch with the government of Algeria to gain a fuller understanding of what took place so that we can work together to prevent tragedies like this in the future."
Earlier Saturday, during a news conference in London with Defense Secretary Leon Panetta, British Defense Minister Philip Hammond called the loss of life appalling and unacceptable.
"It is the terrorists that bear the sole responsibility," Hammond told reporters.
Hammond didn't criticize Algeria's handling of the attack directly, but he appeared to reference the increased concern from world leaders about the lack of transparency in Algeria's anti-terror operation.
"Different countries have different approaches to dealing with these things," he said. "But the nature of collaboration in confronting a global threat is that we work with people sometimes who do things somewhat different, slightly differently from the way we do them ourselves."
Panetta said that "those who would wantonly attack our country and our people will have no place to hide."
"Just as we cannot accept terrorism attacks against our cities, we cannot accept attacks against our citizens and our interests abroad," he said.
Baldor reported from London.