Making the first official US visit to Ukraine since Russia invaded two months ago, Washington's top diplomat and its defense secretary pledged additional military aid, including advanced weapons, and a return of US envoys to Kyiv.
Secretary of State Antony Blinken and Secretary of Defence Lloyd Austin met Ukrainian President Volodomyr Zelenskiy and other top officials in Kyiv late on Sunday, having travelled overland from Poland in a visit designed to show Western support.
US officials said the cabinet secretaries pledged new assistance worth $713 million for Zelenskiy's government and other countries in the region that are fearful of further Russian aggression.
The high-level US visit highlighted the shift in the conflict since Ukrainian forces, armed with a massive influx of weapons from the West, fought off a Russian assault on the capital Kyiv.
Russia has failed to capture any major city since the invasion started on February 24, and having failed to take Kyiv, Russia has concentrated its forces in the south and east, where it has launched an offensive that Zelenskiy dubbed the battle of the Donbas.
Before meeting the US delegation, Zelenskiy on Twitter thanked US President Joe Biden and the United States for leadership in supporting Ukraine.
Earlier, in an emotional address at Kyiv's 1,000-year-old Saint Sophia Cathedral to mark the Orthodox Easter, Zelenskiy said his nation would overcome "dark times".
US diplomats will return to Ukraine in the coming weeks, with Washington announcing a new ambassador.
"There's no substitute for that face-to-face engagement, and of course there is a symbolism to being back in the country," said a State Department official, who briefed reporters in Poland on condition of anonymity.
With a semblance of normal life returning to the capital, several countries have reopened embassies in recent days and some residents who fled the fighting returned for Easter.
Moscow, which describes its actions in Ukraine as a "special military operation", denies targeting civilians and rejects what Ukraine says is evidence of atrocities, saying Kyiv staged them to undermine peace talks.
MORE EQUIPMENT, TALKS
Ahead of the visit by Blinken and Austin, Ukrainian officials drew up a list of weapons urgently needed from the United States, including anti-missile systems, anti-aircraft systems, armoured vehicles and tanks, Zelenskiy aide Igor Zhovkva told NBC News on Sunday.
The United States and NATO allies have shown growing readiness to supply heavier equipment and more advanced weapons systems. Britain has promised to send military vehicles and is considering supplying British tanks to Poland to free up Warsaw's Russian-designed T-72s for Ukraine.
The European Union is preparing "smart sanctions" against Russian oil imports, possibly some form of oil embargo, The Times reported on Monday, citing the European Commission's executive vice president, Valdis Dombrovskis. Read full story
Turkish President Tayyip Erdogan said after talks by phone with Zelenskiy that Ankara was ready to assist in negotiations with Russia. Zelenskiy said he discussed with Erdogan the need for the immediate evacuation of civilians from the southern city of Mariupol, the site of the biggest battle of the conflict.
Russian forces on Sunday again attempted to storm the Azovstal steel plant, the main remaining Ukrainian stronghold in Mariupol, Ukrainian officials said, adding that more than 1,000 civilians are also sheltering there.
Serhiy Volyna, commander of Ukraine's 36th Marine brigade forces in Mariupol, said Russia was hitting the plant with air and artillery bombardments.
"We are taking casualties, the situation is critical... we have very many wounded men, (some) are dying ... the situation is rapidly worsening," Volyna said.
Ukraine on Sunday proposed a "special" round of negotiations with Russia to discuss the fate of the civilians and Ukrainian troops still trapped in the city, though Moscow has yet to respond publicly.
Moscow has previously declared victory in the city and said it did not need to take the steel plant.
Capturing Mariupol would link pro-Russian separatists who control parts of the regions of Donetsk and Luhansk that make up the Donbas with the southern Black Sea peninsula of Crimea, which Moscow seized in 2014.
Ukraine estimates tens of thousands of civilians have been killed in Mariupol and says 100,000 civilians are still in the city. The United Nations and Red Cross say the civilian toll is at least in the thousands.