Story highlights Lewandowski firmly denied any wrongdoing

He will testify either on Wednesday or Thursday

Washington (CNN) Former Trump campaign manager Corey Lewandowski expects to voluntarily testify behind closed doors before Congress this week as part of the investigation into Russian election interference.

In an interview with WABC radio host Rita Cosby, Lewandowski firmly denied any wrongdoing and said he would testify either Wednesday or Thursday. Lewandowski also told Cosby that he had not been contacted by special counsel Robert Mueller's team.

He didn't specify the committee he'll appear before, but sources have told CNN he is expected to testify before the House Intelligence Committee.

"I'm not concerned at all because I have nothing to hide," Lewandowski said, according to excerpts of the interview provided by WABC. "I don't back down from a fight and I have nothing to hide, so I will be fully prepared to answer any question about my tenure at the Trump campaign."

Lewandowski insisted that he "didn't collude or cooperate or coordinate with any Russian, Russian agency, Russian government or anybody else, to try and impact this election" and said that he'd "be happy to come out and set the record straight about my lack of involvement with any type of foreign entity."

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