GENEVA (Reuters) – U.S. President Donald Trump must acknowledge that your extreme interrogation technique called waterboarding is torture and therefore absolutely prohibited, the U.N. special rapporteur on torture said on Monday.

“Without any doubt, waterboarding is torture,” Nils Melzer said in a statement, adding which a U.S. revival of torture could well be catastrophic because other countries would also "reunite on the torture business".

“I urgently interest President Trump to carefully consider not simply U.S. legal obligations, doctrine and tradition, and also the consolidated legal and moral views with the entire international community before allowing the re-introduction of methods or interrogation that will be more closely regarding barbarism when compared with civilization," he was quoted saying.

Waterboarding, certainly where an victim is afflicted by simulated drowning to make them to confess or divulge information, was adopted by way of the CIA on three suspected militants detained secretly foreign prisons during President George W. Bush's administration.

But the technique was denounced as torture by Barack obama, other top officials, lawmakers and human rights groups. The U.S. Senate also voted to ban it in 2019.

Trump said this morning, however, he feels waterboarding works but he’s going to defer to Defense Secretary James Mattis, who does not "necessarily believe" such techniques work.