Boris Johnson will describe Ukraine's resistance to the Russian invasion as the country's "finest hour" when he addresses its parliament later.
Speaking virtually to MPs on Tuesday, he will also set out details of £300m in extra military support.
Downing Street said it would include electronic warfare equipment, a counter-battery radar system, GPS jammers and night-vision devices.
It follows the PM's unannounced visit to Kyiv last month.
Mr Johnson's speech is expected to echo the words of Prime Minister Winston Churchill, just as Ukraine's President Volodomyr Zelensky did when he addressed MPs at Westminster in March.
The prime minister is expected to say that the UK Parliament met throughout World War Two, just as Ukraine's Verkhovna Rada has done through the war with Russia, and the British people showed "such unity and resolve that we remember our time of greatest peril as our finest hour".
"This is Ukraine's finest hour, an epic chapter in your national story that will be remembered and recounted for generations to come," he will say.
"Your children and grandchildren will say that Ukrainians taught the world that the brute force of an aggressor counts for nothing against the moral force of a people determined to be free."
https://www.bbc.co.uk/news/uk-61297478