President Joe Biden has warned that Russia will pay a "severe price" if the country uses chemical weapons in Ukraine.
"I'm not going to speak about the intelligence, but Russia will pay a severe price if they use chemicals," Biden said following remarks announcing further economic moves against Russia.
While the US has so far not presented any evidence that Russia plans to use chemical weapons in Ukraine, the White House, most notably, press secretary Jen Psaki has warned that the weapons could be used in the conflict.
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Russia could use chemical weapons in Ukraine or manufacture a "false flag" operation that uses them, Psaki said Wednesday.
The press secretary, slamming what she called false claims from Russia that the US is developing chemical weapons in Ukraine, tweeted, "Now that Russia has made these false claims, and China has seemingly endorsed this propaganda, we should all be on the lookout for Russia to possibly use chemical or biological weapons in Ukraine, or to create a false flag operation using them. It's a clear pattern."
She also noted Russia's "long and well-documented track record of using chemical weapons" as well as its pattern of "accusing the West of the very violations that Russia itself is perpetrating."
The US government has previously found that the Russian government used chemical weapons in both the 2020 poisoning of Russian opposition leader Alexey Navalny and in 2018 against Sergei and Yulia Skripal in England.
Both determinations by the US led to sanctions under the Chemical and Biological Weapons Control and Warfare Elimination Act, which requires the President to impose economic and diplomatic sanctions if a country is found to have used chemical weapons.
Secretary of State Antony Blinken warned earlier this year of the possibility of Russia carrying out a fake or real chemical weapons attack as a manufactured pretext for an invasion into Ukraine.
But his comments came before Russia's full invasion began.
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Additionally, the US has said that Syria's Bashar al-Assad, whose regime is supported by Russia, has used chemical weapons on its people dozens of times during the war there.
When asked about her tweets at Thursday's press briefing, Psaki declined to speculate on hypotheticals regarding the US response if Russia were to use chemical weapons in Ukraine.
"Well, they have a large biological and chemical weapons program. So it's a pattern, but they also have the capacity. While I'm not going to get into specific intelligence, we look at all of those factors," Psaki told reporters.
She continued, "So the objective (of the tweets) was to make clear the inaccuracy of the information and the misinformation they're trying to put out and make clear to the world that they not only have the capacity, they have a history of using chemical and biological weapons, and that in this moment, we should have our eyes open for that possibility."
She declined to speculate on whether there is any sign of imminent use of chemical weapons by Russia in Ukraine.
Psaki was pressed on whether there will be a military response from the US if Russia were to conduct a chemical weapons attack, she said the current US posture has not changed.
"I'm not going to get into hypotheticals. What we're saying right now is they have the capacity and the capabilities. I'm also not going to get into intelligence," she said.
"But the President's intention of sending US military to fight in Ukraine against Russia has not changed."
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Biden emphasised later Friday that the US will not send ground troops into Ukraine.
"We will not fight the third world war in Ukraine," Biden said during a speech in Philadelphia to the House Democratic Caucus.
He added, "I want to be clear though, we are going to make sure that Ukraine has the weapons to defend themselves of an invading Russian force. And we will send money and food aid to save Ukrainians lives.
"We're going to welcome Ukrainian refugees with open arms if in fact they come all the way here."
During the speech, Biden also thanked Democratic House members for their support of Ukraine, noting he spoke to Ukrainian President Volodymyr Zelenskyy on Friday for about an hour.
Biden added that he speaks to the Ukrainian President "almost daily." Biden stressed how important it is that the US and its allies move together on any moves to counteract the Kremlin.
"I know I've occasionally frustrated you, but more important than us moving when we want to is making sure all of NATO is together, is together - they have different vulnerabilities than we do," Biden said.
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White House stops short of saying Russia is committing war crimes
The White House said Friday that there are "strong indications" that Russia is committing war crimes in Ukraine, stopping short of a declaration, which legally requires an investigation before such an assessment can be made.
"We have all seen the devastating images coming out of Ukraine and are appalled by Russia's brutal tactics," White House deputy press secretary Andrew Bates said.
"Pregnant women on stretchers, apartment buildings shelled, families killed while seeking safety from this terrible violence.
"We are also seeing reports of other types of potential abuses, including sexual and gender-based violence."
He added, "These are disgusting attacks. Civilian casualties are increasing. If Russia is intentionally targeting civilians, that would be a war crime. And as we are all seeing on live television, evidence is mounting and we are documenting it as it takes place.
"There are strong indications that this is occurring and that the heinous way Russia is prosecuting this war will result in war crimes."
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US Ambassador to the UN Linda Thomas-Greenfield became the highest-ranking US official to say that actions committed by Russia against the Ukrainian people constitute war crimes, telling the BBC Thursday, "They constitute war crimes; there are attacks on civilians that cannot be justified by any -- in any way whatsoever."
Other Biden administration officials have not gone as far as to declare outright that Russia has committed war crimes - violations of international laws of armed conflict - and instead have pointed to "credible reports" that such crimes have been carried out and their support for investigations into Moscow's actions.
Vice President Kamala Harris on Thursday referenced "atrocities" committed by the Russians and said that the UN should investigate the allegations of Russian war crimes.
On Friday, Harris said, "We are clear that any intentional attack or targeting of civilians is a war crime. Period."
Bates said the US supports the human rights activists, civil society and independent media documenting, collecting and exposing evidence of possible war crimes, human rights abuses and violations of international humanitarian law.
The US will share that evidence with allies and partners and will "support accountability" with every tool available, "including prosecutions when appropriate," Bates said.
