U.S. political consultant Roger Stone, a longtime ally of President Donald Trump, flatly rejected on Monday all allegations of collusion between the president's associates and Russia during the 2016 U.S. election.

In a 47-page opening statement seen by Reuters before his appearance on Tuesday in a closed hearing of the House of Representatives Intelligence Committee, Stone said he viewed his appearance "as a political proceeding" and criticized some Democratic members of the panel.

Stone accused committee members of making "provably false" statements to create the impression of collusion with Russia.

He also accused the committee of cowardice because he was not allowed to testify in an open forum. He said he wanted the transcript of his interview to be released on the conclusion of his meeting with the committee.

Aides to the committee leaders, Republican Rep. Mike Conaway and Democrat Adam Schiff, declined comment on Stone's statement.

The House panel is one of the main congressional committees investigating allegations that Russia sought to interfere in the 2016 U.S. election and probing whether any Trump associates colluded with Moscow.

U.S. intelligence agencies have concluded that Russia sought to influence the election to boost Trump's chances of defeating former Secretary of State Hillary Clinton, his Democratic opponent.

Russia denies any such efforts, and Trump has dismissed any talk of collusion.

Stone acknowledged his reputation as a tough political strategist, but said he did not engage in any illegal activities.

"There is one 'trick' that is not in my bag and that is treason," he said.