White House press secretary Sean Spicer on April 11 said Adolf Hitler didn't use chemical weapons during World War II. Hitler's regime exterminated millions of Jews in gas chambers. (Reuters)

In criticizing Syrian President Bashar al-Assad's alleged use of chemical weapons, White House press secretary Sean Spicer said Tuesday that even Adolf Hitler did not sink to that level of warfare, despite Hitler's use of gas chambers to kill millions of Jews.

When given the chance to clarify his comment — uttered during Passover, the most celebrated Jewish holiday in the United States — Spicer then said Hitler took Jews “into the Holocaust center” but that Hitler “was not using the gas on his own people in the same way that Assad is doing.”

Spicer brought up Hitler unprompted during Tuesday's White House briefing while emphasizing how seriously the United States takes Assad's use of chemical weapons.

“We didn't use chemical weapons in World War II. You know, you had a, you know, someone as despicable as Hitler who didn't even sink to using chemical weapons,” Spicer said. “So you have to if you're Russia, ask yourself: Is this a country that you, and a regime, that you want to align yourself with? You have previously signed onto international agreements, rightfully acknowledging that the use of chemical weapons should be out of bounds by every country.”

Later in the briefing, a reporter read Spicer's comments back to him and gave him the opportunity to clarify. Spicer's answer only added more confusion.

“I think when you come to sarin gas, there was no — he was not using the gas on his own people the same way that Assad is doing,” Spicer said, mispronouncing Assad's name. “I mean, there was clearly, I understand your point, thank you. Thank you, I appreciate that. There was not in the, he brought them into the Holocaust center, I understand that. What I am saying in the way that Assad used them, where he went into towns, dropped them down to innocent, into the middle of towns, it was brought — so the use of it. And I appreciate the clarification there. That was not the intent.”

When Spicer stumbled further into dangerous territory with this response, the mouth of one White House press aide, seated along the briefing room wall, seemed to fall open in a half gasp.

Before the briefing was even over, White House press aides had realized the magnitude of his mistake — and were working on a response to clarify it. Shortly after he stepped away from the lectern, Spicer put out a statement trying to explain what he meant.

“In no way was I trying to lessen the horrendous nature of the Holocaust,” Spicer said in the statement. “I was trying to draw a distinction of the tactic of using airplanes to drop chemical weapons on population centers. Any attack on innocent people is reprehensible and inexcusable.”

Spicer's comments at briefing sparked outrage and concern. The United States Holocaust Memorial Museum tweeted a video showing footage taken when U.S. forces liberated the concentration camp in Buchenwald, Germany, in April 1945, documenting the atrocities witnessed. Steven Goldstein, executive director of the Anne Frank Center for Mutual Respect and a frequent critic of the president, released a statement accusing Spicer of having “engaged in Holocaust denial, the most offensive form of fake news imaginable, by denying Hitler gassed millions of Jews to death” and called on Trump to fire his press secretary.

Early in the evening, Spicer appeared on CNN to apologize, seeking to put an end to the controversy.

“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 said. “Frankly I mistakenly made an inappropriate and insensitive reference to the Holocaust, for which there is no comparison. And for that I apologize. It was a mistake to do that.”

White House press secretary Sean Spicer apologized for claiming on April 11 that Hitler did not use chemical weapons during WWII, calling it an "inexcusable and reprehensible" mistake on April 12, at a forum on the presidency and the press at the Newseum. (Newseum)

Trump and several people close to him have previously faced accusations of anti-Semitism and making insensitive remarks regarding the Holocaust. During the campaign, Trump tweeted a graphic attacking Hillary Clinton that was circulating in anti-Semitic circles online that featured a Star of David on top of piles of money. Although the image was deleted, Trump later said he wished his staff had left it in place and allowed him to defend it.

After the election, the Anti-Defamation League’s chief executive opposed Trump’s selection of Stephen K. Bannon as his chief strategist because Bannon once led the Breitbart news site, which the organization considers “the premier website of the Alt Right, a loose-knit group of white nationalists and unabashed anti-Semites and racists.”

In January, the White House released a statement on International Holocaust Remembrance Day, which marks the anniversary of the liberation of the Auschwitz concentration camp, that made no mention of Jews or the anti-Semitic views that fueled the Holocaust. At the time, White House spokeswoman Hope Hicks said the omission was intentional because the White House staff is an “incredibly inclusive group, and we took into account all of those who suffered.”

When confronting accusations of anti-Semitism, Trump and those close to him note that his daughter Ivanka, son-in-law and three grandchildren are Jewish. Ivanka Trump posted a family photo on her social media accounts Monday that appears to have been taken at the White House, along with the message: “During #Passover, we reflect on the significance of the exodus from Egypt and celebrate the great freedoms we enjoy today! #ChagPesach.”

On Monday night, the White House hosted a Seder dinner for staff members in the Eisenhower Executive Office Building’s Indian Treaty Room. Trump did not attend and tweeted: “Happy Passover to everyone celebrating in the United States of America, Israel, and around the world. #ChagSameach.” Obama held a Seder in the residence’s Old Family Dining Room all eight years he was president, a new tradition inspired by the Seder he celebrated with three young staffers during the 2008 campaign in the basement of the Sheraton Hotel in Harrisburg, Pa.