MSNBC’s Lawrence O’Donnell issued an apology Wednesday afternoon after President Donald Trump, through his attorneys, demanded the retraction of an unsourced claim that Trump had “Russian billionaires close to Vladimir Putin” as co-signers on loans.

“Last night I made an error in judgment by reporting an item about the president’s finances that didn’t go through our rigorous verification and standards process,” O’Donnell tweeted Wednesday.

“I shouldn’t have reported it and I was wrong to discuss it on the air. I will address the issue on my show tonight,” he added:

Last night I made an error in judgment by reporting an item about the president’s finances that didn’t go through our rigorous verification and standards process. I shouldn’t have reported it and I was wrong to discuss it on the air. I will address the issue on my show tonight. — Lawrence O'Donnell (@Lawrence) August 28, 2019

On Tuesday, O’Donnell cited a “single source close to Deutsche Bank” who claimed that “Russian billionaires close to Vladimir Putin” co-signed on Trump’s loans.

“This single source close to Deutsche Bank has told me that Donald Trump’s loan documents there show that he has co-signers. That’s how he was able to obtain those loans. And that the co-signers are Russian oligarchs,” O’Donnell said.

“If true, that would be a significant factor in Vladimir Putin’s publicly stated preference for presidential candidate Donald Trump over presidential candidate Hillary Clinton,” he continued.

“The source close to Deutsche Bank says that the co-signers of Donald Trump’s Deutsche Bank loans are Russian billionaires close to Vladimir Putin,” he added:

A source close to Deutsche Bank says Trump’s tax returns show he pays very little income tax and, more importantly, that his loans have Russian co-signers. If true, that explains every kind word Trump has ever said about Russia and Putin. @TheLastWord 10pm — Lawrence O'Donnell (@Lawrence) August 28, 2019

Trump, through his attorneys, demanded a retraction, calling O’Donnell’s claims “false and defamatory.”

“These statements are false and defamatory, and extremely damaging,” the president’s lawyer, Charles Harder of Harder LLP law firm, wrote. “The only borrowers under these loans are Trump entities, and Mr. Trump is the only guarantor.”

He continued:

Numerous documents for each of these loans are also recorded, publicly available and searchable online. Thus, actual malice can easily be proven based on your reckless disregard of the truth and unreasonable reliance on an alleged “source” who you will not even identify in your story and likely is seeking to mislead you and the public for political reasons or other ulterior motives. … Demand is hereby made that Mr. O’Donnell and NBCU immediately and prominently retract, correct and apologize for the aforementioned false and defamatory statements.

O’Donnell’s program The Last Word will air Wednesday evening at 10 PM EST.