President Recep Tayyip Erdogan on Saturday, Oct 4 demanded an apology from U.S. Vice President Joe Biden and warned he would become "history for me" over comments in which he said the Turkish leader had admitted that Turkey had made mistakes by allowing foreign fighters to cross into Syria, according to the Associated Press.

Erdogan denied ever saying that and told reporters in Istanbul that Biden "will be history for me if he has indeed used such expressions."

Responding to questions following his speech at the Harvard Kennedy School on Thursday, Biden described Erdogan as "an old friend." Biden added: "He (Erdogan) said: 'You were right. We let too many people through.' Now they're trying to seal their border."

Erdogan said: "I have never said to him that we had made a mistake, never. If he did say this at Harvard then he has to apologize to us."

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.

"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," Erdogan said.

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

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

"The Turks, who are great friends — I have a great relationship with Erdogan, whom I spend a lot of time with — 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? 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-Qaida and the extremist elements of jihadis coming from other parts of the world."