President Volodymyr Zelenskiy says Ukrainians "need to achieve peace" and halt Russian bombardment that has forced millions to flee to countries like Poland, where US President Joe Biden is due to witness the crisis first hand.
On the heels of leaders' summits in Brussels that aimed to show a united Western front against Russia's month-long invasion of its neighbour, President Biden goes to Poland on Friday to meet experts involved in the refugee response.
Western leaders denounced Moscow's invasion as barbaric and promised new military and humanitarian aid after Thursday's talks in Brussels.
The Russian invasion, which President Vladimir Putin calls a "special operation", has killed thousands of people, sent 3.6 million abroad and driven more than half of Ukraine's children from their homes, according to the United Nations.
Zelenskiy said he had made appeals to Western leaders "all for one reason - so that Russia understands that we need to achieve peace. Russia also needs to achieve peace."
"Every day we defend, we get closer to the peace we need so much ... and you can't stop for a minute. Because every minute is about our destiny, it is about our future. About whether we live."
The new Western aid stopped short of Zelenskiy's pleas for a full boycott of Russian energy and a no-fly zone over Ukraine where Moscow's bombs have blasted some residential areas into wastelands.
But in a significant escalation in the lethal aid on offer, a senior US administration official said the United States and its allies were working on supporting Ukraine with anti-ship missiles that could threaten Russian operations in the south.
Ukraine earlier said its forces destroyed a large Russian landing ship, the Orsk, at the southern port of Berdyansk. Video footage showed fire and an explosion, and two vessels, one of which appeared to have been damaged, sailing away as a third burned.
Russia's shelling has been relentless but its armoured columns have barely moved in weeks, stalled near the capital Kyiv.
Ukraine says Russian forces have taken heavy casualties and are low on supplies, and US officials told Reuters that Russia is suffering failure rates as high as 60 per cent for some of its precision-guided missiles.
With stocks of precision-guided munitions running low, Russian forces were more likely to rely on unguided bombs and artillery, Under Secretary of Defence for Policy Colin Kahl said.
The United States accused Russia of committing war crimes in Ukraine, allegations Russia denies.
Ukrainian Deputy Prime Minister Iryna Vereshchuk on Thursday said Russian forces had tortured Ukrainian prisoners. The allegations could not be independently verified, saying:
"We will find every Russian soldier who commits war crimes, along with their accomplices ... do not think that your surnames are unknown to us. No one will be able to escape punishment."
The United States and Britain on Thursday expanded sanctions to new targets and Japan followed suit on Friday, saying it would ratchet up its sanctions and strip Russia of most favoured nation trade status.
But Russian ex-president and deputy head of security council Dmitry Medvedev said sanctions would only unify Russian society. Those targeting wealthy associates of Putin were especially pointless, Medvedev told Russia's RIA news agency:
"Let us ask ourselves: can any of these major businessmen have even the tiniest quantum of influence of the position of the country's leadership? I openly tell you: no, no way."
Weeks of on-and-off peace talks have failed to reach a breakthrough.
In the besieged southern port of Mariupol, which lies between Russian-annexed Crimea and eastern areas held by Russian-backed separatists, thousands are in basements with scant water, food, medicine or power.
Ukraine says it is shifting to the offensive and has pushed back Russian forces in some places.
Civilians have managed to flee through humanitarian corridors negotiated by Ukrainian and Russian officials. Over 3300 escaped on Thursday, officials said.