Republican political operative Roger Stone is so busy preparing for a possible grilling by the US Senate intelligence committee about Russian hacking, that he does not have time to attend the opening of his civil defamation trial in New York City, according to his lawyer.

Stone, a longtime political provocateur and adviser to President Donald Trump, is being sued over a flyer sent to 150,000 New York households during the state's 2010 election that called the Libertarian Party candidate for governor, Warren Redlich, a “sick twisted pervert.”

“This man constitutes a public danger,” said the mailing, which included Redlich's photo and the header “Sexual Predator Alert.” It purported to come from an organisation called People for a Safer New York.

“If you see this man in your neighbourhood, CALL THE POLICE!” it warned.

​Redlich's lawsuit claims that Stone and several accomplices were responsible for the flyer. At the time, Stone was advising two other candidates for governor: Kristin Davis, a former madam of a prostitution ring, and the Republican nominee, Carl Paladino. Redlich also is suing Paladino and his former campaign manager, Michael Caputo.

Stone was subpoenaed to testify in the trial this week, but his lawyer, Benjamin Burge, told the judge Wednesday that he would prefer to appear Monday or Tuesday because he is busy complying with a notice from the US Senate intelligence committee asking him to retain any documents that might be related to its investigation into alleged Russian interference in the 2016 election.

Stone has said he communicated with Guccifer 2.0, the shadowy hacker credited with breaking into the Democratic National Committee's email servers.

“He can't be here until next week,” Burge said of Stone during Wednesday's court hearing.

Justice Richard Braun declined to give him more time, saying Stone must appear whenever he is called as a witness.

Jury selection is scheduled to begin Thursday morning, so opening statements in the trial could start as early as Thursday afternoon. If Stone does not appear, he could face sanctions including a warrant directing a sheriff to bring him to court.

Stone has said in interviews that he was not behind the anti-Redlich flyer. He did not answer calls to his cellphone Wednesday.

Redlich, who is representing himself at the trial, and is seeking unspecified damages, said he wants to call Stone as his first witness.

He said Stone's failure to appear Wednesday was part of a defence strategy to prolong what should be a speedy trial.

“I'm seeing a pattern — delay, delay, delay, delay,” Redlich said.

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Stone, 64, got his start in politics working as a political operative for President Richard Nixon, where he developed a reputation as someone who specialised in campaign trickery and spreading dirt on opponents.

He is the subject of an upcoming Netflix documentary, Get Me Roger Stone.