Britain's Conservative Party annual conference in Birmingham
British Defense Minister Ben Wallace speaks during the annual Conservative Party conference in Birmingham, Britain, October 2, 2022. Reuters

Britain is stepping up its support for Ukrainian soldiers through the winter as a key battle in Kherson looms and as mobilised Russian troops struggle, British Defence Secretary Ben Wallace told Reuters on Wednesday.

Wallace joined NATO Secretary General Jens Stoltenberg to observe the training of Ukrainian troops in the southeast English town of Lydd, as Britain announced the delivery of a further 12,000 extreme cold-weather sleeping kits for Ukraine.

"Winter is approaching and that is an important challenge for both sides," he said. "So we're determined ... to give Ukrainian soldiers the best basic skills because we already know that the Russian military aren't doing that."

Ukrainian forces have piled pressure on Russian troops in the southern region of Kherson that Moscow occupied in February - the only place where Russia has a presence on the west bank of the Dnipro River.

Russia has heavily reinforced its troops there in recent months while Ukrainian forces are trying to advance.

"I wouldn't be surprised if in the next few weeks, we'll see them successfully get to that side of the river," Wallace said of the Ukrainian troops, adding that that was why it was so important to maintain the supply of equipment and support now.

"Ukraine is still making gains in the east of the country, and slowly but surely closing in on Kherson in the south. That's a tough fight."

Stoltenberg, who said NATO allies were also providing support to Ukrainian troops through the winter months, will meet British Prime Minister Rishi Sunak later on Wednesday in London to discuss the future of the defence alliance.

Stoltenberg is the first international leader to visit Sunak in Downing Street, and the meeting comes as Britain looks to update its Integrated Review of defence priorities as the government mulls spending cuts.

Sunak said in a statement that Britain would remain a bedrock of NATO but that the alliance must evolve as challenges change.

Britain is a major contributor to the NATO defence alliance, but public finances are under pressure.

The government will lay out spending cuts and tax rises in a budget on Nov. 17, putting a target to spend 3% of GDP on defence by 2030 in doubt. Wallace said he would continue to fight for defence budgets to modernise his forces.