The United States Tennis Association sent spectators into a state of disbelief when an artist sung the Nazi-era version of Germany's national anthem at a tournament in Hawaii.
Before the Fed Cup match began, the Hawaiian singer performed a rendition of the anthem, included the controversial words, "Deutschland, Deutschland über alles, über alles in der Welt", which translates as "Germany, Germany, above all, above all in the world" at the first round match in Maui.
Although the song was coined before Hitler came to power, that version of the song has become closely related to the horrors of the Third Reich.
Since the end of World War II, the third verse of Deutschlandlied is the only one sung when performing the anthem that was first written in 1922.
After the match, German player Andrea Petkovic wrote on the German federation's website: "I've never felt more disrespected in my whole life, let alone in Fed Cup, and I've played Fed Cup for 13 years now and it is the worst thing that has ever happened to me – horrifying and shocking."
"This is the year 2017 – that something like this happens in America, it can't happen. It's embarrassing and speaks of ignorance," she added, according to a report by German newspaper Bild.
The US Tennis Association extended their "sincerest apologies" for the mistake.
"We extend our sincerest apologies to the German Fed Cup team and all of its fans for the performance of an outdated national anthem prior to today's Fed Cup competition," they said in a statement.
"In no way did we mean any disrespect. This mistake will not occur again, and the correct anthem will be performed for the remainder of this first-round tie."
Germany's own tennis association replied: "We hope so.…"
The USTA quickly responded: "We can assure you that it won't. Again, our sincere apologies."
The Fed Cup is the largest international competition women's tennis, boasting 99 teams in 2015.
Petkovic lost to American player Alison Riske, 7-6, 6-2 in the match.