Ukrainian President Volodymyr Zelensky on Tuesday urged US leader Joe Biden to attend a June peace summit in Switzerland, as he accused Russia's Vladimir Putin of trying to derail the gathering.
Zelensky's appeal came as he locked in a commitment from Belgium to supply 30 F-16 fighter jets by 2028, on the latest leg of a whistlestop tour to rally Western support.
Ukraine is pushing to whip up attendance at the peace conference next month where it hopes to win broad international backing for its vision of the terms needed to end Russia's war.
But the meeting threatens to be overshadowed if key Ukraine backer Biden -- who is locked in campaigning against Donald Trump and has given no sign he would participate -- ultimately stays away.
"If (Biden) is not present, it will be just like applauding Putin: personally applauding and doing so standing," Zelensky said at a press conference alongside Belgium's Alexander De Croo.
The Ukrainian leader said that Putin was "very scared" of the peace summit and was trying to derail the event set for June 15-16.
"He has been trying to thwart this summit and continues to do so," said Zelensky, who has ruled out Russian participation in the gathering.
Moscow meanwhile dismissed the proposed peace summit without Russia as "absurd".
"The conference is, from our point of view, completely hopeless in terms of finding some ways to resolve the conflict around Ukraine," said Kremlin spokesman Dmitry Peskov.
Zelensky's latest tour of allies comes as Ukraine is struggling to hold back a Russian ground offensive in the Kharkiv region, where Moscow recently has made its largest territorial gains in 18 months.
Belgium's commitment of fighter jets -- which it hopes to start delivering by year's end -- came a day after Spain promised Zelensky one billion euros in support on a visit to Madrid, and before he heads to Portugal later Tuesday.
The pledge was made as part of a bilateral security and long-term support accord signed by Zelensky and De Croo, the latest in a string of similar Ukrainian deals with Western backers.
The security agreement, Zelensky said, "includes at least 977 million euros in Belgian military aid to Ukraine this year," in addition to a commitment of support over the next 10 years.
"But let me be very clear, more needs to be done," De Croo said, in a message to Western allies.
"It needs to be done faster, and it needs to be done better. Ukraine can only push back the invader if we provide more and if we provide better arms."
The pledges of further support for Kyiv come as pressure mounts on key allies such as the United States and Germany to let Ukraine hit targets in Russia using weaponry they are supplying.
Washington and Berlin have refused to permit Kyiv to strike over the border out of fear that it could drag them closer to direct conflict with Moscow.
"I think this is unfair," Zelensky said.
"But we, and this is a fact, cannot risk the support of our partners -- that is why we are not using our partners' arms to attack Russian territory.
"That's why we are asking: Please give us the permission to do that."
EU foreign policy chief Josep Borrell threw his weight behind Kyiv's pleas.
"You have to balance the risk of escalation and the need for Ukrainians to defend," Borrell said at a meeting of EU defence ministers across town in Brussels.
That was echoed by NATO boss Jens Stoltenberg who insisted for the second day running that Ukraine had the right to strike "legitimate military targets inside Russia."
But German's deputy defence minister Siemtje Moller reiterated that Berlin had taken a "sovereign decision" not to let Kyiv strike.
And sitting next to Zelensky, even De Croo appeared unmoved as he said the weapons Belgium was supplying could only be used on "Ukrainian territory".
