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Donald Trump has pledged that his presidency would resume waterboarding "or worse" — orders that top CIA officials say would cause heavy resistance from the agency.

"I certainly think many of those who were connected to the [enhanced interrogation techniques] program over its six years' span — and hundreds are still there — would resign or retire rather than having to go down that perilous road again," former CIA lawyer John Rizzo told Newsweek.

While many have debated the extent to which waterboarding is effective (not to mention if such measures violate the Geneva Convention's prohibitions on torture), Trump has insisted that, "It works, okay? It works. Only a stupid person would say it doesn't work." Trump has gone as far as to admit that even if it doesn't work, terrorist suspects "deserve it anyway, for what they're doing."

"I pity the poor SOB who is President Trump's CIA director and gets the order to do interrogation techniques 'worse' than waterboarding, not to mention the CIA general counsel or Justice Department attorney general who has the legal issue dropped in his or her lap," Rizzo said.

One of the CIA's former chiefs, General Michael Hayden, put it in clearer terms in the ABC documentary The Spymasters: "If some future president is going to decide to waterboard," Hayden said, "he'd better bring his own bucket, because he's going to have to do it himself."