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U.S. leader President Barack Obama made sure South Korean pop star Psy knew there were no hard feelings about his past performances at anti-American rallies with a warm handshake in Washington, D.C. on Sunday night.

The Gangnam Style hitmaker performed a Christmas-themed version of his 2012 dance anthem at the White House's annual Christmas in Washington charity concert, just two days after footage of his appearances at anti-U.S. rallies in 2002 and 2004 in South Korea were unearthed online.

Psy, real name Park Jae-sang, publicly apologized to fans following the discovery of the footage, in which he rapped, "Kill those f**king Yankees who have been torturing Iraqi captives/Kill those f--king Yankees who ordered them to torture/Kill their daughters, mothers, daughters-in-law and fathers/Kill them all slowly and painfully."

In a statement, he said, "As a proud South Korean who was educated in the United States and lived there for a very significant part of my life, I understand the sacrifices American servicemen and women have made to protect freedom and democracy in my country and around the world.

"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 innocent Korean civilians that was part of the overall antiwar sentiment shared by others around the world at that time.

"While I'm grateful for the freedom to express one's self I've learned there are limits to what language is appropriate and I'm deeply sorry for how these lyrics could be interpreted. I will forever be sorry for any pain I have caused anyone by those words."

And it's clear Obama has already forgiven and moved on - he greeted Psy onstage at the Christmas concert and gave the grateful singer a hug and a handshake.

Psy, dressed in a sparkly red sweater for the occasion, began his performance in Washington by singing a strained version of The Christmas Song but quickly stopped and told Obama, his wife Michelle, their kids Sasha and Malia and fellow guests, "This is not the reason why I'm here. Let's dance everybody," before breaking into Gangnam Style.

The South Korean hitmaker was joined by Diana Ross, Megan Hilty, Demi Lovato and country singer Scotty McCreery at charity concert, which was held at the National Building Museum in Washington, D.C.