The White House strongly condemned the suicide attack, saying it was "clearly an act of terror", while outgoing Secretary of State Hillary Clinton Clinton spoke with her Turkish counterpart Ahmet Davutoglu on the incident.
"A suicide bombing on the perimeter of an embassy is by definition an act of terror. However, we do not know at this point who is responsible or the motivations behind the attack.
The attack itself is clearly an act of terror," White House Press Secretary Jay Carney told reporters at his daily news conference.
"Clinton spoke with her Turkish counterpart on the terrorist attack," her spokesperson Victoria Nuland said at another news conference.
"She was briefed immediately after the incident and all through the morning. She determined very quickly that she wanted to speak to (US) Ambassador (to Turkey) Francis Ricciardone and the staff and then she wanted to talk to Foreign Minister Davutoglu.
In the conversation with Davutoglu, she obviously expressed condolences for the loss of life. He expressed grave concern for the fact that this had happened," Nuland said.
"She also thanked him for the absolutely excellent cooperation that we've had from Turkish law enforcement. Let me just underscore that point. Turkish national police, in particular, responded immediately and have been cooperating superbly with us," Nuland said.