Former White House chief strategist Stephen Bannon is expected to appear as a witness for the government during Roger Stone's trial next month, a person familiar with the arrangement said Friday.

Bannon was not subpoenaed for his testimony, the person said. Bannon's inclusion on the witness list could indicate that more information about Stone's contacts with the Trump campaign over WikiLeaks may be revealed during the trial.

Bannon appeared to be referenced in special counsel Robert Mueller III's indictment of Stone earlier this year, as a high-ranking Trump campaign official who reached out to Stone "about the status of future releases by" WikiLeaks. The former White House chief strategist has not been charged in relation to Stone's case.