The Gangnam Style rapper has been forced to apologise after YouTube clips emerged of him singing anti-American lyrics and taking part in an anti-American protest.
After a Korean missionary was killed in Iraq in 2004, Psy rapped expletive-laden lyrics from another band's song.
"Kill those bleeping Yankees who've been torturing Iraqi captives," he sung.
"Kill their daughters, mothers, daughters-in-law and fathers."
Another video shows the rapper smashing a model US tank at a protest against the deaths of two South Korean teenagers, who were struck by a US military vehicle.
The videos emerged just days before the viral star's performance at Sunday's White House Christmas concert, that was attended by the Obama family.
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The clips sparked outrage in the US, prompting Psy to apologise.
"The song I was featured in from eight years ago was part of a deeply emotional reaction to the war in Iraq and the killing of two Korean school girls that was part of the overall anti-war sentiment shared by others around the world at that time," he said.
"I will forever be sorry for any pain I've caused by those words."
Psy's Gangnam Style video has been watched about 906 million times on YouTube, becoming the website's most watched clip of all time.