Secretary of State Rex Tillerson is in Moscow meeting with his Russian counterpart Sergey Lavrov amid mounting tensions between the U.S. and Russia over the war in Syria.

On Tuesday, White House officials accused Russia of trying to cover up the Syrian government’s alleged role in last week’s chemical attack, which killed 86 civilians, including dozens of children. While the U.S. asserts the Syrian government carried out the attack, Russia has blamed it on the anti-government rebels. The Russian foreign minister has called the U.S. rhetoric “primitive and loutish.”

Russian President Vladimir Putin has signaled he may meet with Tillerson during the secretary of state’s trip—a reversal from Putin’s earlier position.

Meanwhile, lawmakers and Jewish organizations, including the Anne Frank Center, are calling for White House Press Secretary Sean Spicer’s resignation, after Spicer tried to drum up support for more U.S. military attacks against the Syrian regime by comparing Assad to Hitler and falsely claiming Hitler never used chemical weapons.

Press Secretary Sean Spicer: “You look, 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 the—to using chemical weapons. 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?”

In fact, the Nazis systematically used poison gas as part of its genocide of 6 million Jews and others. The Nazis began experimenting with gas with the specific purpose of carrying out mass murder in the late 1930s. After the Nazis invaded the Soviet Union, they deployed gas vans to kill hundreds of thousands of people. By 1942, the Nazis had set up a series of concentration camps where gas chambers were the main method of killing people. At its peak, as many as 6,000 people, mostly Jews, were gassed to death every day at Auschwitz concentration camp alone.

During his comments, Spicer also referred to Nazi concentration camps as “holocaust centers.”

Hours later, Spicer apologized, although he made a number of mistakes during his apology, including mispronouncing Syrian President Bashar al-Assad’s name.

Press Secretary Sean Spicer: “I mistakenly used an inappropriate and insensitive reference to the Holocaust, for which, frankly, there is no—there is no comparison. And for that, I apologize. It was a mistake to do that. I needed to make sure that I clarified and not was in any way, shape or form any more of a distraction from the president’s decisive action in Syria and the attempts that he’s making to destabilize the region. There’s no way that I can see a stable and peaceful Syria with Bashad al-Asiya—Bashar al-Saad in charge.”

Wolf Blitzer: “Bashar al-Assad. I know you’ve mispronounced his name a few times, but it’s Bashar al-Assad.”

Spicer later said he meant to say President Trump was seeking to stabilize the region, not to destabilize the region.