Ukrainian President Volodymyr Zelenskyy addressed Italy's Parliament on Tuesday, warning that "Ukraine is the gateway to Europe for Russian troops."

He called for more sanctions so Russia "is looking not for military reserves or mercenaries somewhere in Libya or Syria, but for peace."

"This is a war that Russia has been preparing for a long time. Which one person has been preparing for a long time. One! For decades," Zelenskyy said. "Their goal is Europe."

Zelenskyy compared the Russian invasion to the Nazis, saying, "The last one who did something like this in Europe were the Nazis, when they invaded other countries."

-ABC News' Christine Theodorou

For the first time since the invasion of Ukraine, Russia's combat capability has likely fallen below 90%, a senior U.S. defense official told reporters. The official said there are no tangible indications of reinforcements being brought in from elsewhere in the country.

"[This is] combat power that they assembled in Belarus and in the western part of their country prior to the invasion. It is not an assessment of all Russian military power," the official said.

The official said there are "indications" that Ukrainian resistance is trying to retake some territory seized by Russian troops, such as the town of Izyum.

"What we're starting to see are indications that they are now able and willing to take back territory that the Russians have taken," said the official. "Whether this is a part of some sort of larger operational plan, we can't say for sure."

In Mykolaiv, northeast of Odessa, the Russians have been forced to reposition themselves to the area south of the city because Ukrainian resistance was so strong north of the city, the official said.

The logistical and resupply issues continue to plague Russian troops with the official noting that Russia now has concerns about fueling its ships in the Black Sea. Frostbite has also become an issue for Russian troops who continue to be inadequately supplied.

Ukrainian forces have mounted a strong resistance inside of Mariupol against the "significant number" of Russian forces that have made their way into the city, according to the official.

“The Ukrainians are fighting very, very hard to keep Mariupol from falling,” said the official.

Russia has fired more than 1,100 missiles in Ukraine, according to the official.

-ABC News' Luis Martinez

Russia's Defense Ministry claimed its forces pursued the retreating Ukrainian units of the 54th separate mechanized brigade, and advanced 4 kilometers on Tuesday, approaching the settlement of Novomikhailovka.

Russian-backed Donetsk troops took control of the settlement of Verkhnetoretskoe and continues to attack units of the 25th Airborne Brigade of the Armed Forces of Ukraine, according to Russia's Defense Ministry.

Russia claims two tanks, five infantry fighting vehicles, three field artillery pieces and seven off-road vehicles were destroyed.

Russia also claimed it fired air and sea-based high-precision long-range weapons at Ukrainian military facilities. It claimed it destroyed depots of fuel, lubricants, rocket and artillery weapons and ammunition.

The country's defense ministry said its operational-tactical and army aviation hit 83 military facilities of Ukraine. Among them: four command posts, four anti-aircraft missile systems, three depots of rocket and artillery weapons and ammunition, as well as 68 places of military equipment accumulation.

Russia claimed air defense systems shot down 6 Ukrainian unmanned aerial vehicles in the air, including one Bayraktar TB-2 near the village of Merefa, Kharkiv region.

In total, since the beginning of the attack, 236 unmanned aerial vehicles, 185 anti-aircraft missile systems, 1,547 tanks and other armored combat vehicles, 154 multiple rocket launchers, 612 field artillery guns and mortars, as well as 1,343 units of special military vehicles have been destroyed, Russia claims.

Hungarian President-elect Katalin Novak visited the small town of Beregsurany on Tuesday. The town is a mile from the border with Ukraine.

Beregsurany, which has a population of about 600 people, has seen an influx in refugees fleeing Ukraine. Some days as many as 3,000 people pass through it.

The town has responded by setting up a local welcome center to facilitate registration, offering temporary beds until more permanent homes become available and providing counseling and care.

Novak is a member of Hungary’s far right, populist political party and closely works with Prime Minister Viktor Orban, known for his hardline stance on immigration and strict asylum policies.

Novak met with reporters after handing out pancakes to some of the refugees, a tradition started by a group of local women who make hundreds of pancakes daily for everyone coming over the border.

Novak said Hungarians are a welcoming people and want to help those who are fleeing violence and forced to leave their homes.

When pushed on why the politics are different for these refugees, compared to refugees from other countries like Syria, she said Hungary will always welcome people fleeing violence, but the country’s stance on mass migration remains the same.

She did not explain why certain people are considered "mass migration" and others are "seeking asylum."

-ABC News' Maggie Rulli

All Russian troops have left the Ukrainian cities of Kyiv and Chernihiv, withdrawing north toward the borders of Belarus and Russia to consolidate before likely redeploying to the Donbas region in eastern Ukraine, a senior U.S. defense official told reporters Wednesday.

But even with the Russians gone, the territory remains treacherous.

"There are some indications that they left behind mines and things like that, so the Ukrainians are being somewhat careful in some areas north of Kyiv as they begin to clear the ground and clear the territory and re-occupy it," the official said.

While the U.S. hasn't yet seen these troops redeploy elsewhere in Ukraine, it'll likely happen soon, according to the official. Ukrainian forces are preparing for a major fight in Donbas, the official said.

The official also said the Pentagon is "monitoring" an apparent nitric acid explosion in Ukraine's Luhansk region, which Russia blamed on Ukraine.

"We've seen the Russians claim that this was a Ukrainian attack on this. We do not believe that is true," the official said. "We do believe that the Russians are responsible, but exactly what they used when they did it, why they did it, what the damage is, we just don't have that level of detail," the official said.

The official also noted that a small number of Ukrainians currently in the U.S. for "professional military education" were pulled aside for a couple days of training on Switchblade drones, which the U.S. is sending overseas as part of its military aid, according to the official.

"Although it's not a very difficult system to operate, we took advantage of having them in the country to give them some rudimentary training on that," the official said.

-ABC News' Matt Seyler