ABC News chief anchor George Stephanopoulos apologized Friday to his viewers for his failure to disclose $75,000 in gifts he made to the Clinton Foundation while he was covering Hillary Clinton’s presidential campaign and foundation controversies.

Stephanopoulos had apologized Thursday for not revealing contributions initially reported at $50,000.

But an ABC official later told Fox News that the contributions actually totaled $75,000.

Stephanopoulos also pledged not to moderate any Republican presidential debates.

ABC News' chief anchor is a former Bill Clinton spokesman and aide, and his ties to the former first family are well-known. However, as first reported by Politico, he made multiple $25,000 donations to the foundation in recent years -- and while the donations can be found in the organization's records, Stephanopoulos did not disclose them to viewers as he covered the Clintons.

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Even when he interviewed the author of "Clinton Cash" -- the high-profile book examining potential conflicts of interest behind Clinton Foundation funding -- on ABC's "This Week," Stephanopoulos did not disclose his own contributions.

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Sen. Mike Lee, R-Utah, told Fox News that when it comes to reporting on the upcoming White House race, Stephanopoulos perhaps "ought to sit this one out."

Stephanopoulos said in a statement on Thursday: "I made charitable donations to the Foundation in support of the work they're doing on global AIDS prevention and deforestation, causes I care about deeply. I thought that my contributions were a matter of public record. However, in hindsight, I should have taken the extra step of personally disclosing my donations to my employer and to the viewers on air during the recent news stories about the Foundation. I apologize."

Meanwhile, ABC News said they stand behind their star anchor.

A statement from the network said: "As George has said, he made charitable donations to the Foundation to support a cause he cares about deeply and believed his contributions were a matter of public record. He should have taken the extra step to notify us and our viewers during the recent news reports about the Foundation. He's admitted to an honest mistake and apologized for that omission. We stand behind him."

Rich Noyes, research director for the conservative Media Research Center, said the contributions also weren't discussed when Stephanopoulos interviewed former President Bill Clinton in recent years -- but at least should have been disclosed when he interviewed "Clinton Cash" author Peter Schweizer.

"It's especially egregious that he did not talk about this [then] ... That was the time he needed to come clean," he said.  

In that interview, the host of "This Week" posed tough questions to Schweizer, pressing him on whether he really had any "smoking gun" showing wrongdoing by the Clintons in their dealings with foundation donors and in Hillary Clinton's actions as secretary of state.

Noyes said such tough questions would be expected, but viewers might see them differently had the host disclosed his donations. Noyes said he hopes ABC News addresses the issue on air.

Fox News' Ed Henry contributed to this report.