The nearest Russian forces to Kyiv are still about 9 miles to the northwest of the city's center, a senior U.S. defense official told reporters on Thursday. This is the same distance the troops were estimated to be last Friday.

The Russians haven't been able to advance because Ukrainian forces "are very actively resisting any movement," the official said. But Russia maintains an advantage with long-range weaponry, the official added.

While those nearest Russian troops have stalled, other forces are coming to join them, bringing long-range artillery pieces, the official said.

"So it appears that they continue to want to conduct a siege of Kyiv, that's what you want to use artillery for," the official said. "We haven't seen that manifest itself, we're just seeing them move them into place."

The only notable movement since Wednesday is that Russian forces are assessed to have taken control of Izyum, a city in eastern Ukraine, the official said. The Pentagon believes the Russians intend to push south toward Donetsk and Mariupol to seal off the Donbas area, the official said. This could be to prevent Ukrainian troops in the east from moving westward to defend other areas.

Russia has now launched more than 1,000 missiles against Ukraine, up from an estimate of 980 on Wednesday, according to the official. These estimates count missile launches, not necessarily effective hits, the official said.

"We have seen an increase of strikes on civilian infrastructure and civilian targets," the official said, but could not offer numbers.

-ABC News' Matt Seyler

Secretary of State Anthony Blinken said Thursday that he "personally" agrees with President Joe Biden that Russia is committing war crimes by intentionally targeting civilians in Ukraine.

Blinken said State Department experts from the Office of Global Criminal Justice are documenting and evaluating evidence for a formal determination and will share those findings with those responsible for accountability.

"There's going to have to be, one way or another, accountability for this war of aggression," Blinken said.

While Ukrainian officials have been engaged in talks with Russian counterparts, Blinken expressed pessimism about the talks, saying the U.S. hasn't seen "any meaningful effort" by Russia to end the war through diplomacy. If anything, Blinken warned, Russian President Vladimir Putin indicated in his remarks Wednesday that he's doubling down on military aggression.

-ABC News' Conor Finnegan

Twenty-three people were killed and 26 others were wounded from shelling on a school and community center in Merefa, which is near Kharkiv in eastern Ukraine, the Kharkiv Region Prosecutor's Office said.

-ABC News' Fidel Pavlenko

About 400 bulletproof vests that were set to be sent to aid Ukraine were stolen from the Ukrainian Congress Committee of America's headquarters in Manhattan's East Village, according to the New York City Police Department.

No arrests have been made in the burglary, which took place early Wednesday, police said.

-ABC News' Derricke Dennis