Rice, one of three former Obama officials who met with the panel this week, has come under sharp scrutiny from some House Republicans because they believe she improperly "unmasked" -- or revealed the identities collected in intelligence gathering -- of Trump associates in US intelligence reports. She has vigorously denied any wrongdoing.

"Ambassador Rice met voluntarily with the Senate Select Committee on Intelligence today as part of the committee's bipartisan investigation into Russia's interference in the 2016 US presidential election," said Erin Pelton, a spokesperson for Rice, who also served as Obama's US ambassador to the United Nations. "Ambassador Rice appreciates the Committee's efforts to examine Russia's efforts to interfere, which violated one of the core foundations of American democracy."

Rice's appearance Friday marks the latest high-profile witness to privately meet with the panel ahead of the Senate's upcoming summer recess, with investigators meeting with former Obama chief of staff Denis McDonough and James Clapper, who was Obama's former director of national intelligence.