Mykhailo Podolyak, an adviser to Ukrainian President Volodymyr Zelenskiy, said Ukraine's supporters "understand how the war is developing" and the need to supply planes capable of providing cover for the armoured fighting vehicles that the United States and Germany have pledged.
However, in remarks to online video channel Freedom, Podolyak said that some of Ukraine's partners maintain a "conservative" attitude to arms deliveries "due to fear of changes in the international architecture".
Russia and North Korea have accused the US and European countries of prolonging and taking a direct role in the war by sending Ukraine increasingly sophisticated weapons.
"We need to work with this. We must show (our partners) the real picture of this war," Podolyak said, without naming specific countries.
"We must speak reasonably and tell them, for example, 'This and this will reduce fatalities, this will reduce the burden on infrastructure. This will reduce security threats to the European continent, this will keep the war localised.' And we are doing it."
The US and Germany agreed on Wednesday to share advanced tanks with Ukraine along with the Bradley and Marder vehicles promised earlier, a decision that led to criticism not only from the Kremlin but from the prime minister of NATO and European Union member Hungary.
Hungarian Prime Minister Viktor Orban said on Friday that countries providing weapons and money to assist Ukraine in its war with Russia have "drifted" into becoming active participants in the conflict.
Orban has refused to send weapons to neighbouring Ukraine and sought to block EU funds earmarked for military aid.
The Ukrainian foreign ministry said it would summon Hungary's ambassador to complain about Orban's remarks.
Ministry spokesman Oleg Nikolenko reacted after Orban told reporters that Ukraine was "a no-man's land" and compared it to Afghanistan.
"Such statements are completely unacceptable. Budapest continues on its course to deliberately destroy Ukrainian-Hungarian relations," Nikolenko said in a Facebook post.
Foreign weapons have proven essential to Ukraine's defence while stoking ever-higher tensions with Russia.
Russia's defence ministry said on Saturday that Ukrainian forces used US-made HIMARS rockets to strike a hospital in the eastern Ukrainian town of Novoaidar, killing 14 people.
Novoaidar is located in Luhansk province, which is almost entirely under the control of Russian forces or Russian-backed separatists.
The Russian defence ministry alleged the hospital was deliberately targeted.
Its claim of a strike in Novoaidar could not be immediately verified.
Russia bombarded Ukraine with missiles, exploding drones and artillery shells this week.
The attacks continued on Saturday, when Russian missiles struck the city of Kostiantynivka in eastern Ukraine's Donetsk province.
The missiles fell in a residential area, killing three civilians, wounding 14 and damaging four high-rise apartment buildings, a hotel and garages, governor Pavlo Kyrylenko said.
"Kostiantynivka is a city relatively far from the front line but still, it constantly suffers from enemy attacks. Everyone who remains in the city exposes themselves to mortal danger," Kyrylenko said.
Podolyak said Ukraine needs supplies of long-range missiles "to drastically curtail the key tool of the Russian army" by destroying the warehouses where it stores cannon artillery used on the front line.
