Sean Spicer. Joshua Roberts/Reuters

White House press secretary Sean Spicer ducked a series of questions on Tuesday about President Donald Trump's promotion of a Fox News story based on an anonymous source. Days earlier, Trump blasted such stories as "made up."

The Monday Fox News report, which Trump retweeted on Tuesday, laid blame on the Russians rather than Jared Kushner, Trump's son-in-law and senior adviser, for discussing the possibility of a communications back channel between the Trump administration and Moscow. The report cited "a source familiar with the matter."

A Friday report in The Washington Post said Russian Ambassador Sergey Kislyak told Moscow that Kushner was the one who wanted a secret communications channel between Trump's team and the Kremlin. The Post's story cited "US officials briefed on intelligence reports."

On Sunday, Trump tweeted, "Whenever you see the words 'sources say' in the fake news media, and they don't mention names ... it is very possibly that those sources don't exist but are made up by fake news writers."

Both The Post and Fox News relied on anonymous sources for their stories. Trump tried discrediting such sourcing in a series of Sunday morning tweets but retweeted the Fox News story anyway on Tuesday.

Spicer said during Tuesday's press briefing — his first in weeks — that a Post reporter's questions about what Trump knew of the back-channel discussions assumed "a lot of facts that are not substantiated by anything but anonymous sources that are so far being leaked out."

"Your question presupposes facts that have not been confirmed," he said.

Another reporter asked whether Trump's retweeting of the Fox News story meant he confirmed them, listing some of the story's main points.

"I think what I just said speaks for itself," Spicer responded.

The reporter said Spicer was attempting to discredit The Post's anonymous sources while Trump was promoting a Fox story based on a single anonymous source.

"Why are those sources — or this source, rather — that they used more credible than the ones in the Washington Post article?" she asked.

Spicer pivoted to talking about a statement provided by Kushner's attorney that he had already referenced in the briefing and mentioned the dossier prepared by a former British spy that contained unverified claims about Trump's ties to Russia.

"So again, I'm not going to get into confirming stuff," Spicer said. "There is an ongoing investigation."

Reports about the December meeting in Trump Tower between Russians and Trump officials — which was already under scrutiny from investigators — have thrust Kushner into the center of the ongoing Russia investigations.

The FBI is investigating whether any members of Trump's campaign colluded with Russian officials to interfere in the 2016 presidential election. Earlier this month, Trump fired James Comey, the FBI director who was overseeing that investigation. Deputy Attorney General Rod Rosenstein then appointed former FBI Director Robert Mueller as a special counsel to oversee the bureau's Russia investigation.