Russia-Ukraine updates: US sanctions Russian military shipbuilder, diamond miner

White House National Security Adviser Jake Sullivan said Wednesday that the U.S. is looking at the “deliberate drumbeat of misinformation” and propaganda from Moscow, which has “all the markers of a precursor” for them to use chemical weapons.

Earlier, President Joe Biden said there is a "real threat" of Russia using chemical weapons in Ukraine.

Sullivan declined to comment on whether Biden's assessment was based on movements of weapons, or if it was based entirely on state propaganda.

Sullivan also commented on negotiations between Russia and Ukraine and said there are questions about Russia's trustworthiness.

"I will point out that Russia has not been trustworthy in its public statements about its intentions with respect to Ukraine for months. So, we take everything that they say at the negotiating table, or from their podiums, with a very large grain of salt," he said, talking to reporters on Air Force One.

-ABC News' Justin Gomez

The U.S. has assessed that "thousands" of Ukrainian civilians have been killed by the war, Ambassador-at-Large for Global Criminal Justice Beth Van Schaack said at a briefing on Wednesday.

Van Schaack declined to speak to particular incidents that back up this assessment, but when asked about the attack on the Mariupol theater, which had been marked that children were among those sheltering inside, she said it was a civilian target that the Russians should not have hit.

The U.S. earlier formally declared that Russian forces have committed war crimes in Ukraine.

-ABC News' Conor Finnegan

At least 977 civilians have been killed and 1,594 others have been injured in Ukraine since Russian forces invaded on Feb. 24, according to the latest figures from the Office of the United Nations High Commissioner for Human Rights (OHCHR).

"Most of the civilian casualties recorded were caused by the use of explosive weapons with a wide impact area, including shelling from heavy artillery and multiple-launch rocket systems, and missile and air strikes," the OHCHR said in a statement Wednesday.

The OHCHR noted that the actual number of casualties are believed to be "considerably higher," because the receipt of information from some areas with intense hostilities, like the southeastern port city of Mariupol, have been delayed and many reports are still pending corroboration.

Other areas where the number of casualties are still being corroborated include Volnovakha in the Donetsk Oblast, Izium in the Kharkiv Oblast, Sievierodonetsk and Rubizhne in the Luhansk Oblast, and Trostianets in the Sumy Oblast, where there are allegations of numerous civilian casualties, according to the OHCHR. Casualty numbers from these regions are not included.

-ABC News' Christine Theodorou

U.S. Secretary of State Antony Blinken on Wednesday announced that the State Deptartment has made a formal assessment that Russian forces have committed war crimes in Ukraine.

Last week, President Joe Biden said he believed Russia's President Vladimir Putin was a war criminal and Blinken told reporters he personally believed war crimes had been committed. But now, the agency has made a formal determination, Blinken said in a statement.

"Based on information currently available, the U.S. government assesses that members of Russia's forces have committed war crimes in Ukraine," Blinken said, citing a "careful review of available information from public and intelligence sources."

Blinken added: "As with any alleged crime, a court of law with jurisdiction over the crime is ultimately responsible for determining criminal guilt in specific cases. The U.S. government will continue to track reports of war crimes and will share information we gather with allies, partners, and international institutions and organizations, as appropriate."

Blinken said there are "numerous credible reports of indiscriminate attacks and attacks deliberately targeting civilians, as well as other atrocities."

"Russia’s forces have destroyed apartment buildings, schools, hospitals, critical infrastructure, civilian vehicles, shopping centers, and ambulances, leaving thousands of innocent civilians killed or wounded," Blinken said.

-ABC News' Conor Finnegan