Donald Trump said that America is fighting "sneaky, dirty rats" as the country battles Islamic State.
US President Mr Trump told Fox News channel's Sean Hannity that the Islamic extremists were "evil that lurks around the corner without the uniforms".
He appeared to be comparing the situation to World War Two when he said: "Ours is harder because the people we're going against, they don't wear uniforms.
"They're sneaky, dirty rats and they blow people up in a shopping centre and they blow people up in a church.
"These are bad people.
"When you're fighting Germany and they had their uniforms, and Japan and they had their uniforms and they had their flags on the plane, and the whole thing.
"We are fighting sneaky rats right now that are sick and demented. And we're going to win."
Mr Trump's words came just a day after another US channel, ABC News, aired an interview where he hinted that he would be willing to contemplate the use of torture techniques against America's enemies.
His administration is reportedly seeking a review of how the US is conducting its war on terror, including interrogation techniques such as waterboarding and whether CIA "black site" prisons overseas should be reopened.
This was despite CIA director Mike Pompeo previously ruling out using torture, and defence secretary James Mattis telling the President that it is counter-productive.
Mr Trump told ABC News: "When ISIS is doing things that no one has ever heard of, since medieval times, would I feel strongly about waterboarding?
"As far as I'm concerned, we have to fight fire with fire.
"We're not playing on an even field. I want to do everything within the bounds of what you're allowed to do legally.
"But do I feel it works? Absolutely, I feel it works."
Meanwhile, Mr Trump has said the US needs more submarines but he wants to buy them at a lower cost.
He told Fox News: "We're lacking submarines and we're going to build new submarines but the price is too high so I'm cutting the prices way down."
He did not give details on how this would be achieved.
