Roger Stone, a former advisor to President Donald Trump, speaks to the media after leaving the Federal Courthouse on January 25, 2019 in Fort Lauderdale, Florida.

Roger Stone, the self-proclaimed dirty trickster and longtime friend of President Donald Trump, is due to be arraigned Tuesday morning in Washington on federal charges brought by special counsel Robert Mueller.

Stone, who was arrested in Florida on Friday, is expected to plead not guilty to the seven counts against him, including making false statements to Congress, witness tampering and obstructing justice.

Mueller says Stone, 66, lied to Congress about his alleged efforts to have WikiLeaks release material hacked by Russian agents from Democrats, including Hillary Clinton's campaign chairman, during the 2016 campaign that ended with Trump's victory.

A grand jury indictment charges that Stone was in contact with top-ranking Trump campaign officials about efforts to leak damaging information about Clinton right before Election Day.

The indictment also says a senior official in the Trump campaign "was directed" to talk with Stone about potential future releases by WikiLeaks, following a release of stolen Democratic National Committee emails in July 2016:

Stone claims he was merely engaged in constitutionally protected free speech when he touted information about the material in WikiLeaks' possession.

After he was arrested last week, Stone was released on a $250,000 signature bond.

His bail and release conditions could be modified at Tuesday's arraignment in Washington.

"I will plead not guilty," Stone said Friday. "There is no circumstance whatsoever in which I will bear false witness" against Trump, he said.

However, during an interview with ABC News on Sunday, Stone would not rule out cutting a cooperation agreement with Mueller, who has brought criminal charges against former Trump campaign chairman Paul Manafort, the president's former personal lawyer Michael Cohen, and several other people in Trump's orbit. All of those other people have pleaded guilty in various charges.

"If there's wrongdoing by other people in the campaign that I know about, which I know of none, but if there is, I would certainly testify honestly," Stone told ABC News.

"I'd also testify honestly about any other matter, including any communications with the president," he added. "It's true that we spoke on the phone, but those communications are political in nature, they're benign, and there is — there is certainly no conspiracy with Russia."

Mueller is continuing to investigation possible collusion by members of the Trump campaign with Russian efforts to interfere with the 2016 election, and possible obstruction of justice by the president himself.

Trump denies any wrongdoing.