ISTANBUL -- Vice President Joe Biden apologized to the United Arab Emirates on Sunday for charging that the oil-rich ally had supported al-Qaida and other jihadi groups in Syria's internal war, his second apology in two days to a key participant in the U.S.-led coalition against Islamic State extremists.

The White House said Biden telephoned Crown Prince Mohammed bin Zayed of Abu Dhabi to say his recent remarks "regarding the early stages" of the conflict in Syria "were not meant to imply that the Emirates had facilitated or supported" the Islamic State, al-Qaida or other extremist groups.

But his apology, the day after expressing similar regrets to Turkey, left open whether the UAE had supported the rise of al-Qaida during the early stages of the war in Syria.

Biden was answering questions at Harvard University's Kennedy School of Government late last week when he veered off the official talking points to declare, "Our allies in the region were our largest problem" in preventing the spread of al-Qaida in Syria.

"The Saudis, the Emiratis; what were they doing?" he said. "They were so determined to take down (Syrian President Bashar) Assad and have a proxy Sunni-Shia war, 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 (Jabhat) al-Nusra and al-Qaida, and the extremist elements of jihadis coming from other parts of the world."

The UAE foreign minister, Anwar Gargash, on Sunday demanded a formal clarification, saying Biden's remarks were "far from the truth" and gave a "negative and inaccurate impression." The UAE's approach to counterterrorism "recognizes the extent of the danger posed by terrorism to the region and to its people," he said

Biden angered Turkey by quoting President Recep Tayyip Erdogan during their meeting during the United Nations General Assembly.

"President Erdogan told me, 'You were right. We let too many people through. So we're trying to seal the border,' " Biden said.

Erdogan retorted that Turkey had not provided "even the smallest amount of support" to any terrorist organization. As for his reputed confession, he said: "I never admitted any mistake, nor did we tell them that they 'were right' during my visit to the U.S." And he said if Biden didn't apologize, "then he will be history for me."

In his apology to Erdogan, as relayed by the White House, the vice president did not retract the quotation he attributed to the Turkish leader. Instead, he "apologized for any implication that Turkey or other Allies and partners in the region had intentionally supplied or facilitated the growth of ISIL or other violent extremists in Syria."

ISIL is one of several acronyms used to identify the group known as the Islamic State.

The other two countries Biden named were Saudi Arabia, which is about to host the U.S.-funded training of thousands of Syrian rebel fighters, and Qatar, which houses a covert CIA training facility for Syrian rebels.

Biden said Saudi Arabia "has stopped the funding" going to extremists in Syria, and the Qataris "have cut off their support for the most extreme elements of the terrorist organizations." Neither country has publicly demanded an apology so far.

Although senior U.S. officials have hinted at least one Gulf country had been supporting the Nusra Front, the al-Qaida-backed militia in Syria, no one had named the countries in a public forum until Biden. His remarks raised a number of questions: What form did the aid take, how long did it continue and what impact did it have on fighting on the ground?

Biden also took aim at Saudi Arabia's human rights record. He compared the collaboration with Riyadh to World War II, when the United States and Britain made common cause with the Soviet Union under dictator Joseph Stalin.

"We knew Stalin was no-good SOB from the beginning," Biden said, answering a student's question about Saudi human rights practices. "But there is a thing called self-interest."

He said the U.S. criticized the Saudi practice of beheading criminals and not granting equality to women.

"We have not remained silent with Saudi Arabia," he said. "I have certainly not been silent with Saudi Arabia."