President Volodymyr Zelensky used a historic visit to London on Wednesday to urge allies to send combat aircraft to Ukraine and deliver "wings for freedom".
Britain said it would consider the proposal in the "long term", although the United States and other NATO allies remain wary of getting more embroiled in Ukraine's war with Russia.
As the one-year anniversary of Russia's invasion looms and Ukraine braces for a fresh Russian offensive in the east, Zelensky is pushing ever harder for friendly nations to send tanks, jets and missiles.
Britain has offered to train Ukrainian fighter pilots on top of an existing programme that has already prepared 10,000 troops for battle.
Zelensky -- dressed in his usual green fatigues -- received waves of applause as he made a historic address to both the lower and upper houses of the British parliament, on what is only his second overseas trip since the war began.
"I appeal to you and the world... for combat aircrafts for Ukraine, wings for freedom," he said.
Prime Minister Rishi Sunak's office said he had tasked the defence secretary with "investigating what jets we might be able to give but, to be clear, this is a long-term solution rather than a short-term capability."
In the meantime, the new UK training will "ensure pilots are able to fly sophisticated NATO-standard fighter jets in the future", an earlier statement from Sunak's office said.
In London, Zelensky held talks with Sunak and also met with King Charles III -- still dressed in an olive-green sweatshirt -- and thanked him for his support of Ukrainian refugees.
He then visited Ukrainian troops receiving military training in Dorset, southwest England, presenting several with service medals.
Speaking alongside Zelensky in front of a British tank, Sunak said that "nothing is off the table" for Ukraine -- including fighter-combat aircraft.
"Of course they are part of the conversation," he said but held back from giving a concrete commitment to provide fighter planes.
Zelensky said that fighter jets had been discussed and reiterated his call for longer-range missiles.
Russia subsequently said that there would be a "response" from Moscow should Britain supply aircraft to Ukraine.
Zelensky is due in Paris late Wednesday, according to a French government source, while Zelensky confirmed he would meet EU leaders on Thursday.
- 'Accelerated' support -
"(Russian President) Vladimir Putin's aggression cannot be seen in any way to have been successful, and that's why we have accelerated and increased our support militarily for Ukraine," Sunak said earlier in the day.
Moscow said Tuesday that Russian forces were advancing towards Bakhmut and Vugledar -- two key centres of fighting in the eastern Donetsk region of Ukraine, now the flashpoint of the war.
On Tuesday, Denmark, Germany and the Netherlands promised that Ukraine would get at least 100 tanks in the "coming months", as the German defence minister visited Kyiv.
Germany recently gave the green light for Leopard battle tanks to be sent to Ukraine after a tireless campaign by Zelensky and allied countries.
Germany's defence minister said Berlin hoped to deliver the first tank battalion to Ukraine by April.
While Berlin has moved, however, other nations that committed to sending the tanks now appear to be stalling.
Training Ukrainian troops to use any armaments they receive remains a challenge.
Last week, Sunak said sending the UK's Typhoon and F-35 fighter jets to Kyiv would require "months if not years" of training and that he was looking for the most effective way of helping Kyiv secure victory.
- 'Ukraine belongs to Europe' -
The United States has so far rejected any deliveries of F-16 warplanes to Ukraine, but other partners, including Poland, have shown themselves more open to the idea.
Britain also announced a fresh round of sanctions targeting organisations relied on by the Russian military.
Putin, however, remains defiant.
Updated maps of Russia have gone on sale in Moscow bookstores that include four annexed Ukrainian regions: Zaporizhzhia, Kherson, Lugansk and Donetsk. Putin regularly refers to them as "our historical lands".
Ahead of the February 24 anniversary of Russia's invasion, German Chancellor Olaf Scholz said it was clear that Moscow would not win and assured Ukraine its future was in the EU.
"Putin will not achieve his goals -- not on the battlefield and not through a dictated peace. That much, at least, is certain after a year of war," Scholz said in a speech to parliament.
Ukraine's Foreign Minister Dmytro Kuleba said he had held a call with US Secretary of State Antony Blinken on the need for more sanctions and military aid ahead of the anniversary.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)