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

The International Atomic Energy Agency is ready to send experts and equipment to Ukraine to help ensure the safety and security of its nuclear facilities and prevent the risk of a severe accident, Director General Rafael Mariano Grossi said Wednesday.

In a video statement, Grossi said he is gravely concerned about the situation and stressed the urgent need to conclude an agreed framework that would enable the IAEA to provide technical assistance for the safe and secure operation of Ukraine’s nuclear facilities, which include 15 reactors a well as the Chernobyl site.

"I have personally expressed my readiness to immediately come to Ukraine to conclude such an agreement, which would include substantial assistance and support measures, including on-site presence of IAEA experts at different facilities in Ukraine, as well as the delivery of vital safety equipment," Grossi said.

He added: "I hope to be able to conclude this agreed framework without further delay. We cannot afford to lose any more time. We need to act now."

-ABC News' Rashid Haddou

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