Hillary Clinton has a hunch about Donald Trump's mysterious tweet, "covfefe".
"I thought it was a hidden message to the Russians," the 2016 Democratic presidential candidate joked.
The former US first lady and New York senator later turned more serious during an interview at a conference near Los Angeles hosted by tech blog Recode.
She suggested that President Trump and his allies were using Twitter and other social media to sidetrack Americans' attention from the investigations into the influence of Russia during the election campaign or the Republican health care bill.
"You can't let Trump and his allies be a diversion. They are a threat," Mrs Clinton said. "They want to influence your reality. And that is what we're up against and we can't let that go unanswered, whether it's on Twitter, Facebook or anywhere else."
Mr Trump tweeted shortly before 1am that "Despite the constant negative press covfefe". The tweet ended there.
Who can figure out the true meaning of "covfefe" ??? Enjoy!— Donald J. Trump (@realDonaldTrump) May 31, 2017
Mrs Clinton talked at length about Russian involvement in the 2016 presidential contest, referring to US intelligence assessments that Russia not only meddled in the election, but did so to help Mr Trump defeat her.
With multiple investigations under way, she asked: "How did they know what messages to deliver? Who told them? Who were they co-ordinating with, or colluding with?"
To pull it off, Russians would have needed to be "guided by Americans", she added later.
Meanwhile, Donald Trump will announce his decision on whether to pull the United States out of the Paris climate accord during a White House Rose Garden event today.