Reuters was not able to immediately verify the full scope of battlefield successes claimed by Ukraine. The total area cited by Zelenskiy is roughly the size of the Greek island of Crete.
Asked whether Ukraine has reached a turning point in the six-month war, Biden said it was hard to tell.
“It’s clear the Ukrainians have made significant progress. But I think it’s going to be a long haul.”
The White House, which has provided billions of dollars of weapons and support to Ukraine, has said the United States is likely to announce a new military aid package in “coming days”.
Since Moscow abandoned its main bastion in the northeast on Saturday, marking its worst defeat since the early days of the war, Ukrainian troops have recaptured dozens of towns in a stunning shift in battleground momentum.
Russia is almost certainly increasingly sourcing weaponry from other heavily sanctioned states like Iran and North Korea as its own stocks dwindle
Speaking in the central square of Balakliia, a crucial military supply hub taken by Ukrainian forces late last week, Ukraine’s deputy defence minister Hanna Malyar said 150,000 people had been liberated from Russian rule in the area.
“The aim is to liberate the Kharkiv region and beyond - all the territories occupied by the Russian Federation,” Malyar said on the road to Balakliia, which lies 74 km (46 miles) southeast of Kharkiv.
Groups of Ukrainian soldiers smoked, grinned and chatted beside the road to Balakliia, which was littered with charred vehicles and destroyed military hardware.
One soldier was stretched out on the top of a tank like it was his living room sofa.
With Ukraine’s flag flying in the city once again, people clamoured for supplies, and spoke of all they endured.
“I was walking away ... when I saw an armoured personnel carrier coming onto the square with a Ukrainian flag: my heart just tightened up and I began to sob,” Mariya Tymofiyeva, a 43-year-old resident said, her voice trembling with emotion.
Kharkiv regional governor Oleh Syehubov said authorities were trying to record crimes committed by Russians during their occupation of the area, and recover the bodies of victims.
“We’re asking everyone around about all the places of burial which can be found,” he said.
Moscow denies its forces have committed atrocities in areas they have controlled since president Vladimir Putin ordered what he calls a “special military operation” on 24 February.
Meanwhile, repair crews have restored the two main power lines supplying Kharkiv city and its surrounds, power firm Ukrenergo said after Russian shelling caused blackouts.
Kyiv fears Moscow will step up attacks on its energy networks as winter approaches and is pleading for anti-aircraft technology from the West to protect infrastructure.
Russia has likely used Iranian-made uncrewed aerial vehicles in Ukraine for the first time, Britian’s defence intelligence said on Wednesday, after Kyiv reported downing one of the UAVs on Tuesday.
“Russia is almost certainly increasingly sourcing weaponry from other heavily sanctioned states like Iran and North Korea as its own stocks dwindle,” it said in a regular update.
The General Staff of Ukraine’s Armed Forces said on Wednesday that Russian forces had launched three missile strikes, 33 air strikes and fired 58 rocket artillery strikes at military and civilian targets over the past 24 hours.
Russian forces still control about a fifth of Ukraine in the south and east, but Kyiv is now on the offensive in both areas.
Ukrainian presidential adviser Oleksiy Arestovych held out the prospects of moving on the eastern province of Luhansk, which together with Donetsk is known as the Donbas, a major industrial region close to the border with Russia.
“There is now an assault on Lyman and there could be an advance on Siversk,” Arestovych said in a video posted on YouTube. He predicted a fight for the town of Svatovo, where he said the Russians have storage depots.
“And that is what they fear most - that we take Lyman and then advance on Lysychansk and Sievierodonetsk,” he said, referring to the twin cities taken by Russia after fierce fighting in June and July.
On top of the setbacks in Ukraine, Russian authorities are also facing challenges in other former Soviet republics.
About 100 people have been killed this week in the deadliest fighting between Azerbaijan and Armenia since a 2020 war, prompting Putin to appeal for calm.
On Wednesday, shooting broke out between guards patrolling the border between Kyrgyzstan and Tajikistan, Russian news agencies said, citing the Kyrgyz border service.