White House Press Secretary Sean Spicer has apologized for making a comparison to the Holocaust in comments about Syrian President Bashar Assad's use of chemical weapons — remarks that drew instant rebuke from Jewish groups and critics.

Spicer said in an interview with CNN that he was trying to make a point about Assad's use of chemical weapons and gas against his people Tuesday but "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."

During the daily White House briefing, Spicer told reporters that Adolf Hitler "didn't even sink to using chemical weapons." Critics noted the remark ignored Hitler's use of gas chambers to exterminate Jews during the Holocaust.

It was the second day in a row in which Spicer, President Donald Trump's principal spokesman, appeared to struggle to articulate the president's foreign policy at a critical time. The White House generated criticism at the start of the year when a statement on international Holocaust Remembrance Day did not make any reference to Jews.

In the CNN interview, Spicer said his comments did not reflect Trump's views. "My comments today did not reflect the president's, were a distraction from him and frankly were misstated, insensitive and wrong." He added, "Obviously it was my blunder." The interview capped several attempts by the White House to clarify Spicer's statement.

The comparison to World War II appeared to be part of a message the administration was trying to deliver as it explains its tactics in Syria. Defense Secretary Jim Mattis noted in a separate briefing that "the intent was to stop the cycle of violence into an area that even in World War II chemical weapons were not used on battlefields."

After the briefing, Spicer emailed a statement to reporters: "In no way was I trying to lessen the horrendous nature of the Holocaust. 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."

His comments -- during the Jewish festival of Passover, prompted anti-defamation groups and Democrats to call for the already embattled press secretary's resignation.

"Sean Spicer must be fired, and the President must immediately disavow his spokesman's statements," said top Congressional Democrat Nancy Pelosi. "Either he is speaking for the President, or the President should have known better than to hire him."

Spicer -- the most public face of the Donald Trump's administration after the president himself -- has is a frequent target of ire and satirists for his angry denunciations press coverage and sometimes loose grasp of the facts.