LONDON: Britain announced an immediate surge of military deliveries to Ukraine to help it fend off an intensifying Russian offensive and pledged to train its pilots as Ukrainian President Volodymyr Zelenskiy arrived in London on a rare visit abroad.

Zelenskiy was due to travel onto Brussels on Thursday where the European Union is holding a summit, according to an EU diplomat. London was his first stop on only his second trip abroad since Russia invaded Ukraine on Feb. 24 after a visit to the United States in December.

In Britain, he will meet Prime Minister Rishi Sunak and King Charles and address parliament.

"The United Kingdom was one of the first to come to Ukraine's aid. And today I'm in London to personally thank the British people for their support and Prime Minister Rishi Sunak for his leadership," Zelenskiy wrote on Telegram, under a photo of him and Sunak at the airport.

Britain, which has been training Ukrainian troops, said the extra training would ensure Ukrainian pilots were able to fly "sophisticated NATO-standard fighter jets in the future", adding the move was "part of long-term investment in their military".

The wording seemed to suggest that Britain had not yet changed its mind on whether to provide Kyiv with the fighter jets it has asked for - something the government has said is not the right approach for now.

Sunak said the visit was a testament "to his country's courage, determination and fight and ... to the unbreakable friendship between our two countries".

"I am proud that today we will expand that training from soldiers to marines and fighter jet pilots, ensuring Ukraine has a military able to defend its interests well into the future."

Zelenskiy will meet King Charles later on Wednesday, a spokesperson for Buckingham Palace said. Charles, who has visited several organisations who help Ukrainians in Britain, has called Russia's invasion of Ukraine a "brutal aggression".

Britain also set out further sanctions to target those who have helped Russian President Vladimir Putin, including manufacturers of military equipment and eight individuals who helped "maintain wealth and power amongst Kremlin elites".

SUNAK PLEDGES MORE SUPPORT

Zelenskiy, who had close ties with ex-prime minister Boris Johnson, visits Britain at a time when Russia is bringing tens of thousands of recently mobilised troops to the battlefield to try to break through Ukrainian defences in eastern Ukraine.

Ukraine's allies have promised hundreds of tanks and armoured vehicles to help Kyiv resist the assault and recapture territory, but have said it will take time to train Ukrainian forces to use them effectively.

Since Johnson resigned last year, Sunak has pledged to continue to support Ukraine, visiting Kyiv in November to tell the Ukrainian leader: "We are with you all the way."

In London, he is expected to tell Zelenskiy he will accelerate the delivery of military equipment to Ukraine.

Britain has trained 10,000 Ukrainian troops brought to battle readiness in the last six months and will train a further 20,000 soldiers this year, the government said.

Last week, Ukrainian troops arrived in Britain to learn how to command Challenger 2 tanks and Sunak will offer to provide Ukraine with longer range capabilities, the statement said.

London has so far refused to deliver fighter jets, saying it was not "the right approach" for now. But defence minister Ben Wallace has suggested that stance could change.

Sunak's spokesman said last week that the quickest a pilot could learn to fly a British fighter jet was 35 months. "We will continue listening to the Ukrainians and consider what is right for the long term," he said.