Russian forces severed the electricity to the Chernobyl nuclear power plant but there is "no immediate risk" of a radiation leak, International Atomic Energy Agency (IAEA) Director-General Rafael Mariano Grossi told ABC News in an interview Wednesday at the agency’s headquarters in Vienna.

There is active fuel at the site of the original reactors that melted down in 1986 but, for the time being, at least, there is enough capacity to cool spent nuclear fuel.

"There is no immediate risk in the dimensions that were imagined and there is work in progress to restore the electrical capacity," Mariano Grossi said. Still, he conceded, "It's a situation that is very fragile."

The lack of reliable electricity also impedes monitoring abilities, leaving the IAEA -- the nuclear watchdog of the United Nations -- occasionally blind to any spontaneous increase in radiation.

"We do have communications and then we lose. Then we recover it. It's not good in terms of following the safety, the security," Mariano Grossi said. "I'm concerned. I’m worried."

There are no IAEA inspectors on the ground while the fighting rages. The director-general said he would not send them in unless he can go first.

"I will not put my staff in harm’s way before me going first," Mariano Grossi said.

Russia is in control of Chernobyl and a second nuclear power station in Zaporizhia. For a time, neither plant had a way to exchange workers or upgrade staffing.

In Zaporizhia, Mariano Grossi said, a shift change is now happening. In Chernobyl, workers are not allowed off-site.

"We all need a break and especially people who are manning extremely sophisticated equipment. The stress is very high," he said.

Mariano Grossi is traveling Thursday to Turkey, where the Russian and Ukrainian foreign ministers will meet face-to-face for the first time since the two-week-old invasion began. He said he will ask each side to commit to "fundamentals," including respecting the physical security of each of Ukraine’s four nuclear power stations, plus Chernobyl.

"We haven't seen something as critical and worrying as a fire breaking out in a building adjacent to a nuclear reactor," Mariano Grossi said. "What really worries me is that unlike Fukushima (in Japan), where you had mother nature to blame, now it would be us."

-ABC News' Aaron Katersky and Robert Zepeda

House Minority Leader Kevin McCarthy broke with former President Donald Trump on Wednesday when he was asked whether he supported Trump's comments praising Putin as a "genius."

“I do not think anything is savvy or genius about Putin," McCarthy, R-Calif., said during a news conference. "I think Putin is evil, he is a dictator and I think he is murdering people right now."

On Feb. 23, a day before the start of the Russian invasion of Ukraine, Trump praised Putin and slammed his successor President Joe Biden in an appearance on a conservative talk radio program.

"This is genius. Putin declares a big portion of the Ukraine ... Putin declares it as independent. Oh, that's wonderful," Trump said of the Russian president's decision to recognize the two provinces of the Donbas Region of eastern Ukraine as independent republics and claimed rebels there asked him to send troops into Ukraine to protect them from Ukrainian military attacks.

Secretary of State Antony Blinken called on the Kremlin to immediately allow Ukrainian civilians to safely depart the cities and towns of Ukraine that are besieged by Russian forces.

Blinken accused Russia of destroying critical civilian infrastructure and blocking people's safe exodus, describing the Kremlin's proposed corridors to Russia "absurd" and "offensive” in a press conference Wednesday.

"Russia's relentless bombardment, including of civilians trying to flee, prevents people from safely escaping the hellish conditions that they've created,” Blinken said.

-ABC News' Conor Finnegan

While Poland has been welcoming refugees fleeing the destruction in Ukraine, the country will eventually meet its limit on how many people it can take in, Konrad Fijolek, president of Rzeszow, Poland, a city about 60 miles from the Ukrainian border, told ABC News.

Like many cities that border Ukraine, Rzeszow, a town of about 180,000 people, has become a pathway to safety and a lifeline for millions of refugees flooding across the border from Ukraine.

Poland will be able to receive about 1.5 million people, but any more will put the country under strain, Fijolek said.

"If a million or more come, we won't be able to cope," he said.

Some estimates suggest as many as 4 million people could leave Ukraine due to the conflict, but most of the major cities in the country are already full — and officials are attempting to move refugees into smaller cities, a feat that is "not easy," Fijolek said.

So far, all the shelters set up in Poland are temporary, he added.

"We would like to avoid the view of refugee camps here," he said. "We would like people who are escaping from the war to think that what awaits here is proper camp not camps."

In addition, the mental state among the people in Poland is continuing to deteriorate, Fijolek said.

"We as local leaders would like to send the message that if there's any possible action to stop the war [find it] and then try to negotiate, because every day at the border we can see the human tragedy," he said.

-ABC News' Chris Donato and Marcus Moore

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