Former U.S. national security adviser Susan Rice believes U.S. President Donald Trump's days in office are numbered — but she predicts his ouster will be through the ballot box, rather than impeachment.

Rice, who was also ambassador to the United Nations under Barack Obama, thinks "Democrats are likely to win" the 2020 election, pointing to Trump's track record.

"I think that the American people have seen a lot of Donald Trump now and much of the downside of his leadership, which is rife with dishonesty, rife with self-interest," Rice told The National's Adrienne Arsenault, in an interview promoting her new book, Tough Love.

But despite what appears to be evidence of "very serious abuses of power" on Trump's dealings with Ukraine, she doesn't think Trump being booted from office through impeachment is likely. However, she does think the impeachment inquiry can inform U.S. voters about Trump's conduct as they cast their ballots for president.

"I think it will deepen concerns among the American public," she said.

Rice also had some warnings for Canada's "tough situation" with China.

On Canada's arrest of Huawai executive Meng Wanzhou at the behest of the U.S., Rice said it was the right thing to do — pointing to extradition agreements between the North American neighbours — and adds that "it's not beneficial for Canada to back down" to Beijing.

"I think Canada should stand by its principles and and be very clear, as you have with other important players like Saudi Arabia," Rice said.

"I don't think Canada benefits from caving," she said, acknowledging that there are detained Canadians in China.

"In my experience [with China] if you give 'em an inch, they'll take a mile."