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The United States believes Kyiv can win the war against Russia if it has the "right equipment", Pentagon chief Lloyd Austin said on Monday.
A landmark visit by Austin and Secretary of State Antony Blinken to Ukraine came as the war entered its third month, with thousands killed and millions displaced by the fighting.
"The first step in winning is believing that you can win. And so they believe that we can win," Mr Austin told a group of journalists after he and Blinken met Mr Zelenskyy.
"We believe that we can win, they can win if they have the right equipment, the right support."
At the meeting, Ukraine pressed the West for more powerful weapons against Russia’s campaign in the Donbas region of eastern Ukraine, where Moscow’s forces sought to dislodge the last Ukrainian troops in the battered port of Mariupol.
“You can’t come to us empty-handed today, and we are expecting not just presents or some kind of cakes, we are expecting specific things and specific weapons,” he said.
The meeting between the two sides lasted three hours and was "very productive and detailed", according to a Pentagon spokesman, adding that Zelenskyy was also briefed on a security summit in Germany on Tuesday among Western allies.
Following the talks, Mr Austin said the US hoped the Russian military would be exhausted in Ukraine, preventing it from launching further invasions.
"We want to see Russia weakened to the degree that it can't do the kinds of things that it has done in invading Ukraine," said Austin.
The US has been a leading donor of finance and weaponry to Ukraine and a key sponsor of sanctions targeting Russia, but had not yet sent any top officials to Kyiv, while several European leaders have travelled there to underscore their support.
"Many countries are going to come forward and provide additional munitions and howitzers. So we're going to push as hard as we can, as quickly as we can, to get them what they need," Mr Austin later said in reference to Tuesday's summit in Germany.
US diplomats will begin a gradual return to Ukraine this week and announced $700 million (653 million euros) in additional military aid.
The highly sensitive trip by two of President Joe Biden's top cabinet members came as fighting continued across swathes of Ukraine, casting a long shadow over Easter celebrations in the largely Orthodox country.
Following a weekend full of fighting, at least five people were killed and another 18 injured on Monday after a Russia rocket attack targeted railway infrastructure in the central Ukraine region of Vinnytsia.
Russian forces have been widely accused of targeting civilian infrastructure throughout the Kremlin's two-month military assault on its pro-democratic neighbour, allegations Moscow denies.
The attacks came as Russia's defence ministry announced a ceasefire around the sprawling Azovstal steel plant in Mariupol, following calls over the weekend to pause fighting to allow civilians to leave.
Moscow has identified Kherson as a vital focal point for its invasion as it seeks to establish a southern land corridor that would link the mainland to the Crimean Peninsula, which it seized from Ukraine in 2014.
Kherson, which has a population of 300,000 people, became one of the first cities to become contested during the devastating conflict which has now entered its third month.
"Russia previously held an illegitimate referendum on the accession of Crimea into the Russian Federation in 2014 to retrospectively justify its seizure of the Peninsula," the UK's Ministry of Defence said on Twitter.
The UK's Defence Secretary Ben Wallace told MPs on Monday that 15,000 Russian personnel have been killed during their offensive.
“Alongside the death toll are the equipment losses and in total a number of sources suggest that to date over 2,000 armoured vehicles have been destroyed or captured," he told MPs.
He reiterated Russia has so far “failed in nearly every one of its objectives”, adding: “In recognition of this failure the Russian high command has regrouped, reinforced and changed focus to securing Donetsk and Luhansk oblast.”
Mr Zelenskyy’s last face-to-face meeting with a top US official was on February 19 in Munich with Vice President Kamala Harris.
While the West has funnelled military equipment to Ukraine, Mr Zelenskyy has stressed repeatedly it needs more heavy weapons, including long-range air defence systems, and warplanes.
Speaking from Kyiv’s ancient St. Sophia Cathedral, Mr Zelenskyy, who is Jewish, highlighted its significance to a nation racked by nearly two months of war.
“The great holiday today gives us great hope and unwavering faith that light will overcome darkness, good will overcome evil, life will overcome death, and therefore Ukraine will surely win” he said.
But the war cast a shadow over celebrations.
In the northern village of Ivanivka, where Russian tanks still littered the roads, Olena Koptyl said: “The Easter holiday doesn’t bring any joy. I’m crying a lot. We cannot forget how we lived.”
Victor Lobush of Kyiv said Ukraine needed more weapons and financial support, and for western nations “not to buy even a drop of the Russian oil".
“Actions, not words, are needed,” Mr Lobush said on Independence Square.
Mr Wallace claimed Ukrainian forces have been using Starstreak high-velocity and low-velocity anti-air missiles for more than three weeks.
He said: “In response to indiscriminate bombing from the air and escalation by President Putin forces on March 9, I announced the UK would supply Starstreak high-velocity and low-velocity anti-air missiles.
“I am able to now report to the House that these have been in theatre for over three weeks and have been deployed and used by Ukrainian forces to defend themselves and their territory.”
Defence Secretary Ben Wallace said Stormer armoured vehicles will give Ukrainian forces “enhanced, short-range anti-air capabilities both day and night”.
Mr Wallace told the Commons that “as we can see from Ukrainians’ requests, more still needs to be done”.
He added: “So, for that reason I can now announce to the House that we shall be gifting a small number of armoured vehicles fitted with launchers for those anti-air missiles.
“The Stormer vehicles will give Ukrainian forces enhanced, short-range anti-air capabilities both day and night.”
He added in the Commons: “At the start of this conflict Russia had committed over 120 battalion tactical groups, approximately 65% of its entire ground combat strength.
“As of now we assess around over 25% of these have been rendered not combat effective.
“Ukraine is an inspiration to us all. Their brave people have never stopped fighting for their lands. They have endured indiscriminate bombardment, war crimes and overwhelming military aggression but they have stood firm, galvanised the international community and beaten back the army of Russia in the north and the north east.
“We anticipate this next phase of the invasion will be an attempt by Russia to occupy further the Donbas and connect via Mariupol the Crimea so it’s urgent that we in the international community ensure Ukraine gets the aid and weapons it so much needs.”