US President Donald Trump and Ukrainian President Volodymyr Zelenskiy agreed Wednesday to work together to end Russia's war with Ukraine, in what the White House described as a "fantastic" one-hour phone call.In their first conversation since an Oval Office meeting descended into a shouting match on February 28, Zelenskiy thanked Trump for US support and the men agreed that technical teams would meet in Saudi Arabia in the coming days.Zelenskiy asked Trump for more air defence support to protect his country against Russian attacks and the US president said he would help locate the necessary military equipment in Europe, the White House said.Trump briefed Zelenskiy on his phone call on Tuesday with Vladimir Putin, at which the Russian president rejected a proposed full 30-day ceasefire sought by Trump and accepted by Ukraine, but agreed to pause attacks on energy infrastructure.That narrowly defined pause appeared in doubt on Wednesday, however, with Moscow saying Ukraine hit an oil depot in southern Russia while Kyiv said Russia had struck hospitals and homes, and knocked out power to some railways.Still, the two sides announced they had carried out a prisoner exchange, each releasing 175 troops in a deal facilitated by the United Arab Emirates. Moscow said it freed an additional 22 wounded Ukrainians as a goodwill gesture.Zelenskiy, describing his conversation with Trump as "positive, very substantive and frank," said he had confirmed Kyiv's readiness to halt strikes on Russian infrastructure and its commitment to an unconditional ceasefire on the front line as the US proposed earlier.Zelenskiy said the US should be in charge of monitoring any ceasefire.The Kremlin said it had called off planned attacks on Ukraine's energy infrastructure, including by shooting down seven of Russia's own drones heading towards Ukraine. It accused Kyiv of failing to call off its own attacks in what it called an attempt to sabotage the agreement.Some European leaders said Putin's rejection of Trump's proposed full truce was proof Moscow was not seeking peace. The offer to temporarily stop attacking Ukrainian energy facilities counted for "nothing" and Trump would have to win greater concessions, Germany's defence minister said.The EU's foreign policy chief Kaja Kallas said she would present a proposal to European leaders in Brussels on Thursday to provide Ukraine with 2mn rounds of large-calibre artillery ammunition.