President Donald Trump has spoken out about revelations tying Hillary Clinton's presidential campaign to a dossier of allegations about his ties to Russia.
On Wednesday, the president said it was a "disgrace" that Democrats had reportedly helped pay for research that produced the document.
He told reporters: "It's just really - it's a very sad commentary on politics in this country."
Trump's comments came one day after news reports said that the Clinton campaign and the Democratic National Committee, for several months last year, helped fund research that ultimately ended up in the dossier.
The document, compiled by a former British spy and alleging a compromised relationship between Trump and the Kremlin, has emerged this year as a political flashpoint.
Law enforcement officials have worked to corroborate its claims.
James Comey, FBI director at the time, advised Trump about the existence of the allegations, and the ex-spy who helped assemble the document, Christopher Steele, has been questioned as part of an ongoing probe into possible coordination between Russia and the Trump camp.
Trump has derided the document as "phony stuff" and "fake news" and portrayed himself on Wednesday as an aggrieved party, posting on Twitter a quote he said was from Fox News that referred to him as "the victim".
The new disclosure about the dossier's alleged origins is likely to fuel complaints by Trump and his supporters that the document is merely a collection of salacious and uncorroborated claims.
"Well, I think it's very sad what they've done with this fake dossier," Trump said, adding without elaboration that "they paid a tremendous amount of money".
He contended that Democrats had initially denied any connection to the document, but now, "they admitted it, and they're embarrassed by it".
A source told the Associated Press that the funding arrangement was brokered by Marc Elias, a lawyer for the campaign and the DNC, and his law firm of Perkins Coie. The deal began around last spring, when the firm was approached by Fusion GPS, the political research firm behind the dossier, and lasted into the autumn, right before election day, according to the source.
When Fusion approached Mr Elias, it had already been doing research work on Mr Trump for a client during the Republican primary. The identity of the original client has not been revealed, although the president hinted on Wednesday that he might know the identity and that it could eventually become public.
It is unclear what Fusion GPS had dug up by the time law firm hired it in April 2016, or how much money was involved in the transaction.
Mr Elias did not immediately return an email seeking comment, and representatives of Fusion GPS declined to comment. The Washington Post first reported the funding deal.
In a statement on Tuesday night, a DNC spokeswoman said the chairman, Tom Perez, was not part of the decision-making and was unaware that Perkins Coie was working with Fusion GPS.
"But let's be clear, there is a serious federal investigation into the Trump campaign's ties to Russia, and the American public deserves to know what happened," the statement said.
Former Clinton campaign spokesman Brian Fallon said on Twitter that he regretted not knowing about Mr Steele's hiring before the election, and that had he known, "I would have volunteered to go to Europe and try to help him".
"I have no idea what Fusion or Steele were paid but if even a shred of that dossier ends up helping Mueller, it will prove money well spent," he wrote in another tweet.