PSY is apologising to Americans for participating in anti-US protests several years ago.
Park Jae-sang, who performs as PSY, issued a statement on Friday after reports surfaced that he had participated in concerts protesting the US military presence in South Korea during the early stages of the Iraq war.
At a 2004 concert he rapped about killing "Yankees" who have been torturing Iraqi captives and their families.
The 34-year-old Gangnam Style rapper said the protests were part of a "deeply emotional" reaction to the war and the killing of two Korean schoolgirls.
He said he "will forever be sorry for any pain I have caused by those words."
Earlier, the White House confirmed President Barack Obama and his family will attend a charity concert on December 21 where PSY is scheduled to perform.