Washington (CNN) Roger Stone vowed Friday afternoon to fight the charges brought by special counsel Robert Mueller and said he would refuse to testify against President Donald Trump.

"I will plead not guilty to these charges. I will defeat them in court," the longtime Trump ally and Republican political operative told reporters gathered outside a federal courthouse in Florida after his arrest early Friday morning. "I believe this is a politically motivated investigation."

"There is no circumstance whatsoever under which I will bear false witness against the President, nor will I make up lies to ease the pressure on myself," he said, sometimes being drowned out by cheers from supporters and chants of "lock him up" from protesters outside the courthouse. "I look forward to being fully and completely vindicated."

Asked later if he was cooperating with the special counsel, Stone said, "I don't want to address that question, but I have made it clear I will not testify against the President, because I would have to bear false witness against him."

Leaving the courthouse, Stone, who once worked for President Richard Nixon, threw up the "V" for victory signs with his hands, a gesture made famous by the former president who resigned over the Watergate scandal.

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