"It really is painful to myself because that obviously was not my intention".
Spicer had appeared on CNN in an interview with Wolf Blitzer to apologize Tuesday afternoon.
While Hitler is believed not to have used chemical weapons on the battlefield, the Nazis used Zyklon B and other types of poison in gas chambers to kill millions of Jews in concentration camps.
While Donald Trump's press secretary Sean Spicer was being drubbed for his Hitler chemical weapons gaffe, Boris Johnson was probably praying that the nearly identical comments he made in 2013 wouldn't resurface.
While he confirmed Mr Trump had not spoken to him directly about the gaffe, he refused to say if the United States president had passed on a message to him. Spicer reiterated that sentiment at Wednesday's forum.
His comments were made at a press conference during a discussion on chemical weapons attacks on Syrian civilians blamed on Syrian President Bashar al-Assad.
The attack in northern Syria left almost 90 people dead, and Turkey's health minister said tests show sarin gas was used. Turkey said sarin gas was used. "There was clearly. I understand your point, thank you". You know, I hope each person can understand that part of existing is understanding that when you do something wrong, if you own up to it, you do it. "You know, you had a - you know, someone as despicable as Hitler who didn't even sink to the - to using chemical weapons".
"To make a gaff and a mistake like this is inexcusable and reprehensible", said Spicer.
Tyga handcuffed and taken to police station, but avoids DUI
There are reports that Tyga was actually arrested, but it's unclear if he was arrested, or just taken into custody at this time. Footage shows police speaking to Tyga in front of fans before he gets led into the back seat of the police vehicle .
Reaction from around the world continued Wednesday. There is no comparing atrocities.
"We did not use chemical weapons in World War II".
Democrats and Jewish organisations condemned Mr Spicer's comments. House Minority Leader Nancy Pelosi called for Spicer's dismissal. "He admitted it", Coffman said, before clarifying: "I mean, he needs to go".
Some are calling on Spicer to resign or be fired.
He also said that there was an overuse of anonymous sources, and suggested that numerous sources were misinformed because they are several steps removed from what is actually happening.
Spicer's comments came on the first day of Passover, drawing swift and stinging reaction from members of the Jewish community, many of whom called on the president to fire him.
And while the ADL acknowledged his apology, it said it wasn't enough - especially after an earlier misfire where Spicer defended a White House Holocaust Remembrance Day statement that failed to mention Jews.
"From a professional standpoint, I think the president has had a successful couple of weeks", he said.