WASHINGTON - White House Press Secretary Sean Spicer apologized for saying Adolf Hitler didn't resort to using chemical weapons like Syria's president, after an outpouring of criticism from politicians and Jewish groups on Tuesday, including calls for his removal from his position.

Spicer made the remarks during a daily press briefing while addressing the chemical attack and Russia's position on it. The White House accused Russia on Tuesday of covering up in a cover-up of the chemical attacks in Syria.

"We had 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 want to align yourself with?"

The Nazis, in fact, did use gas, Zyklon B, to commit mass murder in death camps during the Holocaust. Both Minority Leader Rep. Nancy Pelosi and the Anne Frank Center has called on President Donald Trump to fire Spicer for denying or downplaying the Holocaust.

Spicer tried to clarify his comment later in the press briefing. Hitler "was not using the gas on his own people the same way Assad is doing," Spicer said, adding that the Nazis only used chemical weapons in "Holocaust centers," evidently referring to death camps.

After attempting to clarify his remarks, Spicer apologized in an interview with CNN's Wolf Blitzer. "Frankly, I mistakenly made an inappropriate and insensitive reference to the Holocaust, for which there is no comparison," Spicer said. "And for that I apologize. It was a mistake to do that."

Spicer added that he was aware of the use of gas chambers during the Holocaust, saying that he should have remained focused on Assad at the press briefing and asking people to forgive him for his mistake.

"My goal now and then is to stay focused on Assad and I should have," he said. "I realized that I had made a mistake and I didn't want to be a distraction to the President's agenda." Spicer added that he did not want his comments to distract from Trump's attempts to "destabilize the region."

According to Politico, after backlash from Jewish groups over the comments, Spicer called the offices of Sheldon Adelson to apologize: "Sean called shortly after and said he made a terrible mistake and apologized if he was offensive," a statement for the Republican mega-donor said.

Before Spicer made his apology, Israeli Transportation Minister Yisrael Katz called Spicer's comment "serious and outrageous... We have to demand that he apologize, or resign," Katz tweeted.

After the apology, Katz told Army Radio that "I thought it was my responsibility as a Jew and the son of a holocaust survivor to respond and commended these statements. I thought that Israel should demand he apologize or quit and overnight I see that he did apologize and we welcome this."

The Anne Frank Center demanded President Donald Trump to fire Spicer for "engaging in Holocaust denial."

"Spicer's statement is the most evil slur upon a group of people we have ever heard from a White House press secretary," the Center's Executive Director Steven Goldstein said, adding that Spicer lacks the integrity to serve in his role.

Minority Leader Rep. Nancy Pelosi also called for Trump to fire Spicer. “While Jewish families across America celebrate Passover, the chief spokesman of this White House is downplaying the horror of the Holocaust.

“Sean Spicer must be fired, and the President must immediately disavow his spokesman’s statements. Either he is speaking for the President, or the President should have known better than to hire him,” Pelosi said in a statement.

Jeremy Ben Ami, the president of the dovish Jewish advocacy group J Street, took to Twitter to express his outrage:

The National Jewish Democratic Council criticized Spicer's comment, calling it "inappropriate and insulting."

"And yet, it’s unsurprising, especially given this administration’s tendency to be too casual when it comes to their relationship with the Jewish community," the NJDC said in a statement.

"We demand a full apology and a promise that these sorts of dangerous comparisons by the Trump administration are over."

Democrats didn't spare Spicer, either. "Someone get @PressSec a refresher history course on Hitler stat #Icantbelievehereallysaidthat," Sen. Ben Cardin tweeted.

Rep. Ted Deutch, a Democrat from Florida, wrote that "whether ignorant or cruel, Spicer's comments must be condemned" by Trump. He added that Spicer "needs to visit [the U.S.] Holocaust Museum for a powerful dose of reality." Deutch was part of a bipartisan group of Congress members devoted to fighting anti-Semitism, that visited the museum just last week. He told Haaretz during that visit that fighting anti-Semitism and educating people about the Holocaust has to be a bipartisan commitment in the United States.

Representatives from a number of leading Jewish-American organizations told Haaretz they could not comment on the statement because of Passover, but will address it right after the holiday.

While the Holocaust Museum has yet to issue a statement, an archivist with the museum tweeted: