(CNN) -- U.S. Vice President Joe Biden apologized to Turkey's leader on Saturday for saying that President Recep Erdogan admitted his country had made mistakes allowing foreign fighters to cross into Syria. The apology came hours after Erdogan expressed his anger over the comments to reporters in Istanbul, saying "Biden has to apologize for his statements." Or Biden, he said, will become "history to me," according to published reports by the semi-official Anadolu news agency. The problem appears to have originated during a question-and-answer session following a speech this week at the John F. Kennedy School of Government at Harvard University when Biden was asked about Turkey and the threat posed by the so-called Islamic State terror group, known as ISIS or ISIL.
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Turkey's President Recep Erdogan demanded an apology from Vice President Joe Biden
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Erdogan was angered by comments Biden made
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Biden said Erdogan told him that Turkey had let too many people through the border
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Erdogan told reporters Biden must apologize or he will be "history to me"
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"The Vice President made clear that the United States greatly values the commitments and sacrifices made by our Allies and partners from around the world to combat the scourge of @placeholder, including Turkey."
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"The Vice President made clear that the United States greatly values the commitments and sacrifices made by our Allies and partners from around the world to combat the scourge of ISIL, including @placeholder."
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The issue has arisen at a sensitive time, with @placeholder's government authorizing the use of military force against terror groups, including ISIS as its fighters laid siege to towns just south of the Turkish border.
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The government also agreed to allow foreign troops to launch operations against @placeholder from Turkey.
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The government also agreed to allow foreign troops to launch operations against ISIS from @placeholder.
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While @placeholder is known for making blunt statements that sometimes embarrass the administration, Turkey is particularly sensitive to allegations of allowing terrorists to cross its border into Syria.
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Turkey, in turn, has accused @placeholder of fomenting the unrest that has led to ISIS taking hold in the region.
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Turkey, in turn, has accused Syria of fomenting the unrest that has led to @placeholder taking hold in the region.