Vice President Biden on Saturday apologized to Turkey President Recep Tayyip Erdogan for saying the Turkish leader admitted his country made mistakes by allowing foreign fighters to cross into Syria.

Biden spoke directly to Erdogan to “clarify” comments made on Thursday at Harvard University and apologized for “any implication" that Turkey or other allies had intentionally supplied or helped in the growth of the Islamic State or other extremists groups in Syria, the White House said.

Erdogan denied making such remarks and said Biden would become "history to me" over the comments at Harvard’s Kennedy School of Government, in Cambridge, Mass., unless he fixed the situation.

The speech was an especially bad event for the vice president who has a history of gaffes and unscripted, problem-causing remarks.

Biden also took a question from a student who identified himself as being the vice president of the student body by jokingly saying first: Ain't that a b-tch? … I mean ... excuse me, the vice president thing?”

In 2010, after President Obama signed the Affordable Care Act into law on national TV, Biden was caught on a live microphone saying to the president this is "a big f---ing deal."

Biden on Thursday also described Erdogan as "an old friend" but suggested he said privately: “You were right. We let too many people through.”

Turkey is now trying to seal its border.

Erdogan also said: "I have never said to (Biden) that we had made a mistake, never. If he did say this…, then he has to apologize to us.

"Foreign fighters have never entered Syria from our country. They may come to our country as tourists and cross into Syria, but no one can say that they cross in with their arms."

He said Turkey had prevented 6,000 suspected jihadis from entering the country and deported another 1,000.

The spat comes as Turkey, a NATO ally, is expected to define the role it will play in the U.S.-led coalition against the Islamic State militants who have captured a swath of Iraq and Syria, in some cases right up to the Turkish border.

This week Turkey's parliament approved a motion giving the government powers for military operations across the border in Syria and Iraq and for foreign troops to use Turkey's territory.

A day earlier, Biden and Erdogan held a telephone discussion on ways their countries can work together to degrade and destroy Islamic State and restore security and stability to the region, according to the White House.

At Harvard, Biden said that "our biggest problem is our allies" in responding to the civil war in Syria.

"The Turks … the Saudis, the Emiratis, etc. What were they doing? They were so determined to take down (Syrian President Bashar) Assad and essentially have a proxy Sunni-Shia war," Biden said.

"What did they do?” he continued. “They poured hundreds of millions of dollars and thousands of tons of weapons into anyone who would fight against Assad -- except that the people who were being supplied were al Nusra and al Qaeda and the extremist elements of jihadis coming from other parts of the world."

The White House also said in readout of the Biden-Erdogan conversation Saturday: "The two leaders reaffirmed the importance of Turkey and the United States working closely together to confront ISIL," as Islamic State is also known.

The Associated Press contributed to this report.