A senior U.S. defense official told reporters Friday that there is still "no appreciable movement" by a convoy of Russian forces approaching Kyiv, with the closest forces still about 25 kilometers from the city.

The official said a sabotaged bridge and Ukrainian attacks have contributed to the stalling of the convoy.

As for Kharkiv and Cherniv, the official said the U.S. estimates that Russian forces are about 10 kilometers from both city centers.

The official confirmed Russia took control of the Zaparozhye nuclear power plant.

The official said the U.S. is not in a position to independently verify that Russia has taken control of Kherson, saying fighting between the Russians and Ukrainians around the city has been seen as recently as today.

Mariupol is still under Ukrainian control, but Russians are bombarding the city and approaching from the north and up from the Azov coast, the official said.

Ukraine is still assessed to have "a strong majority" of its combat air power in tact, according to the official. Both Ukraine and Russia are also both believed to be using drones.

Russia has sent in approximately 92% of the forces it had arrayed at the border, up from about 90% yesterday, the official said.

Russians have now fired more than 500 missiles against Ukraine, according to the official.

-ABC News' Matt Seyler

The United Nations Security Council met Friday in an emergency session over Russia's attacks on Ukraine's Zaporizhzhia nuclear power plant.

The British representative said this is the first time a state has attacked a functioning nuclear power plant.

Senior U.N. diplomat and Under Secretary-General for Political Affairs Rosemary DiCarlo condemned active military activity near a nuclear site as "not only unacceptable, but highly irresponsible."

"Every action should be taken to avoid a catastrophic nuclear incident," she added, saying an attack on a functioning nuclear power plant is contrary to international humanitarian law.

-ABC News' Conor Finnegan

A new Russian law could send people to prison for up to 15 years for posting "fake news" about the war.

Journalists and media in Russia will now only be able to report what is happening as the Kremlin reports it.

Duma, Russia's legislative body, passed the rule Friday. It will be sent to Russian President Vladimir Putin's desk for it to be signed into law.

-ABC News' Tanaya Stukalova

The Arctic Council on Friday said it would boycott future talks with Russia over its invasion of Ukraine. Russia currently holds the chairmanship until 2023, according to a report by Reuters.

The intergovernmental forum is designed to promote cooperation between the eight Arctic states of Canada, Denmark, Finland, Iceland, Norway, Russia, Sweden and the U.S.

The council said it is canceling all of its official meetings, including those of its subsidiary bodies, until further notice. Its next meeting was scheduled in Russia this May.

This comes at a sensitive time when climate change is opening up the Arctic to resource exploitation.

-ABC News' Tracy Wholf

The Russian forces charging toward Kyiv haven't made progress in the last day as they face Ukrainian resistance and low food and gas supply, a senior U.S. defense official told reporters Tuesday.

However, it could be a deliberate pause, the official said. "Part of the stall could be ... as a result of their own self-determined sort of pause in operations -- that they are possibly regrouping, rethinking, reevaluating," the official said.

The U.S. believes Russian forces "have committed now more than 80% of what was their pre-staged combat power," the official added.

The official said some Russian soldiers weren't told they were going into combat. The official said "not all of them were apparently fully trained and prepared."

The strong Ukrainian resistance has also hurt morale, according to the official.

Russia has now launched more than 400 missiles on Ukraine, the official said. The U.S. believes Russia has launchers that could be used for thermobaric weapons, but cannot confirm their use, the official said.

Russian forces are making the most progress in the south. Russians are attacking Kherson in south Ukraine, which "appears very much to be contested city at this point," the official said.

Russians are also approaching Mariupol in southeastern Ukraine, and while they haven't yet entered the city, "they are close enough now that they could attack Mariupol with long range fires," the official said.

Two towns on the path to Mariupol are believed to be occupied by the Russians, according to the official.

The U.S. believes the Russians hope to move north out of Mariupol up to the heavily-contested city of Kharkiv. The official said they believe Russian forces are trying to encircle Kharkiv.

The U.S. official noted that they've seen "certain risk-averse behavior by the Russian military" over the last week.

"Take the amphibious assault, for instance. They put those troops ashore a good 70 kilometers away from Mariupol because they knew Mariupol was going to be defended and they could put them ashore in an uncontested environment. And they still haven't reached Mariupol," the official said.

"They are not necessarily willing to take high risks with their own aircraft and their own pilots," the official said.

"And of course we're seeing that on the ground -- the fairly slow and steady progress that they have made, and you guys are seeing it for yourselves on the ground where ... units are surrendering, sometimes without a fight."

-ABC News' Matt Seyler