Bolton Rice Vanderbilt FILE
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.

Rice pointed to the fact that a number of Bolton’s former subordinates on the National Security Council, like Lt. Col. Alexander Vindman and Fiona Hill, testified during the House impeachment probe and were subsequently attacked. Both had received subpoenas. Vindman was fired from the White House in recent weeks and was reassigned to the Pentagon.

“That, to me, makes it even more difficult, as a former national security adviser, not being willing to come forward,” Rice said. “I would feel like I was shamefully violating the oath that I took to support and defend the Constitution against all enemies foreign and domestic.”

In response, Bolton downplayed the impact his testimony would have made on the outcome of the impeachment trial. After the President was impeached by the House, he was acquitted by the Senate in an almost entirely party-line vote. Sen. Mitt Romney of Utah was the only Republican to find Trump guilty of one article of impeachment, abuse of power.

“I will bet you a dollar right here and now my testimony would have made no difference to the ultimate outcome,” Bolton said Wednesday. “If anybody thinks to the contrary, I just don’t think you knew what was going on in Washington.”

Bolton would not say if he would testify if subpoenaed now by the House, citing the prepublication review process of his forthcoming book. For weeks, he and his lawyers have been embroiled in a battle with the White House over the contents of the book, which is due to be published in March – the administration is raising concerns about the publication of classified information that it says is protected by executive privilege.

“I’ve done the best I could in difficult circumstances,” Bolton said. “I sleep at night because I have followed my conscience.”

CNN’s Vivian Salama and Kylie Atwood contributed to this report.