Nashville (CNN) Former national security adviser Susan Rice did not mince words in telling her former Trump administration counterpart John Bolton what she would have done about testifying as part of the impeachment process.

"I thought a lot about if I had been in that position how would I have approached it, and I'll be honest: It's inconceivable to me that if I had firsthand knowledge of gross abuse of presidential power that I would withhold my testimony from a constitutional accountability process," said Rice, who served in the Obama administration, Wednesday while sitting next to Bolton at an event at Vanderbilt University in Nashville.

Bolton, whose upcoming book is poised to contain details about President Donald Trump and his pressure campaign in Ukraine , did not provide testimony to either the House or Senate as part of the President's impeachment. At Wednesday's event, Bolton noted that he had not been subpoenaed for such information.

"In no case did I say I would reject a subpoena," he said.

"I can't imagine withholding my testimony with or without a subpoena," Rice countered.

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