After Ukrainian President Volodymyr Zelenskyy told ABC News’ David Muir that he believes President Joe Biden can do more to facilitate getting Polish fighter jets to Ukraine, the Biden administration said it is ultimately up to Poland.

“This is Poland’s sovereign decision to make,” White House press secretary Jen Psaki told ABC News’ Cecilia Vega. “We have in no way opposed Poland transferring planes to Ukraine.”

Psaki said there are “practical questions” to consider, such as how the planes would be transferred and where they would depart from and land. She also noted that procuring new planes and transferring serious weapons systems often takes years -- so a speedy transfer would represent a major challenge.

Vega asked Psaki if it was just logistical issues or whether Biden was concerned that supplying planes to Poland would “exacerbate the conflict.”

The press secretary said there are logistical challenges and that they’re “looking at all of those factors.”

“But we are not certainly preventing or blocking or discouraging Poland,” Psaki said. “That is, they are a sovereign country. They make their own decisions, but it is not as easy as moving planes around.”

-ABC News’ Sarah Kolinovsky

New York City has gone from a "high alert" to an "ultra-high alert" for potential cybersecurity attacks on critical city infrastructure following the Russian cyber-aggression in Ukraine, a New York Police Department official said Monday.

NYPD Deputy Commissioner John Miller said during a news conference that normally the city is on "high alert" for cyberattacks, but a difference between "high" and "ultra-high" alerts is that they can attribute possible cyber threats to "state actors." When tensions rise between the United States and Russia, so does the threat for tactical and strategic cyberattacks, Miller said.

"There is no guarantee that those attacks will be limited to Ukraine," Gillibrand said. "The decision to impose sanctions on Russia puts the country at an increased risk that Russia will carry out retaliatory cyberattacks, particularly against New York state infrastructure and individuals."

When asked during the news conference if there have been any potential direct Russian cyberattacks against New York, New York City Chief Technology Officer Matthew Fraser said, “we have seen an uptick [in cyber threats], but we are not aware of any campaign that's explicitly targeting the city itself."

-ABC News' Victoria Arancio

A senior U.S. defense official said on Monday that Russian President Vladimir Putin has committed nearly "100% of his combat power" into Ukraine.

"We now assess that Mr. Putin has committed nearly 100% of his combat power into Ukraine. And by combat power, I mean that combat power that he had amassed along the border with Ukraine and in Belarus," the defense official said.

The official also said reports that Russia is attempting to recruit Syrians to sign up and fight in Ukraine appear to be accurate.

"We find that noteworthy that he (Putin) believes that he needs to rely on foreign fighters to supplement what is a very significant commitment of combat power inside Ukraine as it is," the official said.

The official said Russia has launched more than 625 missiles against Ukraine since the invasion began on Feb. 4. He said Russia has increased its use of "long-range fires" to compensate for a lack of movement in its forces on the ground.

"So, we certainly have noticed increases in what we call long-range fires -- bombardment, rocket attacks, artillery, as well as missile strikes," the official said.

-ABC News' Matthew Seyler

The third round of cease-fire talks between Ukraine and Russia took place in Belarus Monday and produced incremental steps forward, according to the lead Ukrainian negotiator.

Following the meeting, the third in eight days, lead Ukrainian negotiator Mykhailo Podolyak tweeted, "There are small positive movements forward in improving the logistics of humanitarian corridors... Intensive consultations have continued on the basic political block of the regulations, along with a ceasefire and security guarantees."

Ukrainian authorities have claimed efforts to evacuate its citizens out of the country have been disrupted by Russian forces shelling the humanitarian corridors Moscow agreed to in a cease-fire.

-ABC News' Patrick Reevell

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