President Donald Trump has called for "an immediate investigation" into senior Democrat Charles Schumer's ties to Russian resident Vladimir Putin.
The president tweeted a photo of the two men holding coffee and doughnuts at a New York City petrol station and called the Senate Minority Leader "a total hypocrite".
Mr Trump did not say where the photo came from but Mr Schumer quickly pointed out that it was taken in 2003 when Mr Putin ventured to New York to celebrate the opening of a Russian-owned Lukoil petrol station in Manhattan.
Mr Schumer, in his own tweet, said he would "happily talk" under oath about his meeting with Mr Putin, which took place "in full view of press and public".
He then challenged Mr Trump to do the same and a short time later posted a follow-up in which he further poked fun at the photo, noting: "And for the record, they were Krispy Kreme donuts."
On the same trip to the United States in 2003, Mr Putin travelled to Camp David, Maryland, where he met with Republican president George W Bush and the two held a joint news conference.
Mr Trump's tweet came just hours after the conservative website Drudge Report made the photo its lead image.
And that was a day after the photo was unearthed by the pro-Trump blog Gateway Pundit, which ran it with the headline "Where's the outrage?"
Trump targeted congressional Democrats for their encounters with Russians over the years even though the party's criticism of Attorney General Jeff Sessions centred on his failure to acknowledge his meetings when questioned at his Senate confirmation hearing and in written responses to the Judiciary Committee.
"I think he was asked a pretty straightforward question at his committee hearing and I do think he should resign," Senator Bernie Sanders said in an interview.
Mr Trump also tweeted on Friday about House Minority Leader Nancy Pelosi, who was among the first to call for Mr Sessions to resign.
In his tweet, Mr Trump linked to a 2010 photo in which Ms Pelosi and other lawmakers are shown meeting with Russian officials, including then-president Dmitry Medvedev and ambassador Sergey Kislyak.
Mr Trump demanded an investigation of the House minority leader. Ms Pelosi had initially denied ever meeting Mr Kislyak but her spokeswoman later clarified that they never had a one-on-one meeting.
Ms Pelosi then needled Trump by saying he did not "know the difference" between an official meeting photographed by the press and a "secret" meeting that Mr Sessions "lied about under oath".
Mr Sessions said on Thursday he would recuse himself from Russia probes after it was revealed that he had conversed with Russia's ambassador twice during last year's campaign, a contradiction of his testimony during his Senate confirmation hearings.
But that move has not satisfied many Democrats, who have called for Mr Sessions's resignation. They also demanded an independent investigation into the Trump campaign's ties to Russia.