"We can confirm a terrorist blast at a checkpoint on the perimeter of our embassy compound in Ankara, Turkey, at 1:13 p.m., local time," U.S. State Department spokeswoman Victoria Nuland said. "We are working closely with the Turkish national police to make a full assessment of the damage and the casualties."
Officials said the guard and suicide bomber were killed. It had been reported earlier that two security guards died in the attack.
The explosion destroyed a door at the entrance and scattered masonry from the wall around it but embassy workers said there was no damage inside the building, the Hurriyet Daily News reported. Embassy personnel were taken to safe rooms within the building.
White House Press Secretary Jay Carney called the bombing "an act of terror."
"[A] suicide bombing on the perimeter of an embassy is by definition an act of terror," he said during the daily briefing. "However, we do not know at this point who is responsible or the motivations behind the attack."
He said the United States would work with Turkish authorities in the investigation and offered condolences to the families of those killed or injured.
"Turkey remains one of our strongest partners in the region, our NATO ally. We have worked shoulder-to-shoulder with the Turks to counter terror threats," Carney said. "[This] will only strengthen our resolve."
The attack on the embassy in Ankara came just over 4 1/2 months after heavily armed militants stormed the U.S. Consulate in Benghazi, Libya. Four Americans died in that Sept. 11 attack, including U.S. Ambassador Chris Stevens.