Donald Trump opened the door to torturing terrorism suspects if he's elected president, telling ABC News Sunday that waterboarding "doesn't sound very severe" given the barbarism of ISIS.

Here's what Trump said in a telephone interview with ABC's Jonathan Karl.

JON KARL: Would President Trump authorize waterboarding and other enhanced interrogation techniques, even torture? DONALD TRUMP: I would be inclined to be very strong. When people are chopping off other people's heads and then we're worried about waterboarding and we can't because ... I have no doubt that that works. I have absolutely no doubt. JON KARL: So you'd bring back water-boarding? DONALD TRUMP: You mentioned waterboarding, which was such a big subject. I haven't heard that term in a year now, because when you see the other side chopping off heads, waterboarding doesn't sound very severe.

In his first week in office in 2009, President Barack Obama banned the CIA's use of waterboarding and other brutal treatment of detainees, vowing that the United States "will not torture."

A Senate Intelligence Committee report released in December 2014 revealed gory details of the CIA's treatment of detainees, including the insertion of hummus into one prisoner's rectum. The committee concluded that none of it worked.

"The committee finds, based on a review of CIA interrogation records, that the use of the CIA's enhanced interrogation techniques was not an effective means of obtaining accurate information or gaining detainee cooperation," the panel wrote.

Trump is the leader in GOP presidential primary polls, including a Wall Street Journal/NBC News survey released Sunday that shows him with 19 percent backing, compared with 15 percent for Wisconsin Gov. Scott Walker and 14 percent for former Florida Gov. Jeb Bush.

The aggressive stance on torture probably won't hurt Trump in the Republican primary — and it may help him. In December 2014, 73 percent of Republicans told CBS News pollsters that enhanced interrogation techniques are sometimes justified.