The German citizen, who was not identified, "died at the Embassy building at approximately 1:00 pm under circumstances that indicate a possible suicide," the Embassy statement said. "We would like to express our heartfelt condolences to the family of the deceased."
It said police would release more details at a later time, but a Berlin police spokesman declined the comment on the incident.
"We do not release any information on suicides," he said.
Earlier the website of news magazine Der Spiegel reported that the victim was a guard at the embassy and had shot himself in a men's toilet. The report cited security sources as saying that by the time officers arrived at the scene the man was dead.
The new US Embassy opened last year next to the Brandenburg Gate, one of the city's main tourist attractions.