Amid gaffe, White House Press Secretary Sean Spicer apologised on Tuesday after saying Adolf Hitler did not use chemical weapons during World War II, a media report said.

In an effort to shame Russia's alliance with Syrian President Bashar al-Assad and his use of chemical weapons, Spicer, while talking to the press had said that Hitler "didn't even sink to using chemical weapons" during World War II, almost immediately attracting criticism from the journalists.

The comment was immediately decried and after a series of attempts to clear up his words, Spicer apologised in an exclusive interview with CNN.

"I was obviously trying to make a point about the heinous acts that Assad had made against his own people last week, using chemical weapons and gas," he cleared during the interview.

"Frankly, I mistakenly made an inappropriate and insensitive reference to the Holocaust, for which there is no comparison and for that I apologise. It was a mistake to do that," Spicer said.

Spicer, who said he was "aware" that gas chambers were used during the Holocaust, later said he should have "stayed focused" on Assad and asked people to forgive him for his "mistake."

"My goal now and then is to stay focused on Assad and I should have," he said, adding, "I realised that I had made a mistake and I didn't want to be a distraction to the President's agenda."

While Hitler did not use chemical weapons on the battlefield, Hitler and the Nazis used gas chambers to exterminate Jews, disabled people and others.