Ukraine can count on the UK’s support, James Cleverly told Ukrainian President Volodymyr Zelensky during his second visit to Kyiv.
The meeting in the war-torn nation’s capital came amid signs the expected Ukrainian counter-offensive against the Russian invasion may have started.
The UK is preparing to host a conference focused on Ukraine’s economic recovery in London later in June.
In a video posted to Mr Zelensky’s Facebook page, Mr Cleverly is heard saying that the UK “will continue backing you and your country until you are victorious”.
The Ukrainian president thanks the UK for the “big support” it has given his country.
He wrote on Facebook: “During the meeting, we discussed important topical issues: Ukraine’s expectations from the Nato Summit in Vilnius, promotion of the Ukrainian peace formula and preparation of the global summit on its implementation, as well as the London international conference on the reconstruction of Ukraine.
“We are very grateful for the support that the UK has provided and continues to provide to Ukraine.”
Kyiv has long called for Ukraine to be admitted to Nato, but allies are divided about when and how any accession might happen as the war with Russia continues.
Prime Minister Rishi Sunak last week said Ukraine’s “rightful place” is in Nato, at a gathering of European leaders in Moldova ahead of the key meeting of Nato leaders in Lithuania in July.
In the video from Kyiv, the Foreign Secretary is seen speaking of his previous visit to Ukraine last November when it was “cold and it was dark”.
“But this time I can see there’s more life in the city. The traffic is heavier, which normally is a bad sign in a city. But I think for me it demonstrates what I mean to be true.
“And that is that the Ukrainian people are not going to allow themselves to be broken by this.”
“When we made the commitment publicly that we will continue backing you and your country until you are victorious in your self-defence, we meant it. When we said that we would do more and go further, we meant it.”
Russia has kept up a steady barrage on the Ukrainian capital and other parts of the country in recent weeks as Kyiv has been readying what it says is a counter-offensive to push back Moscow’s troops, 15 months after their full-scale invasion.
Ukraine has not confirmed claims by Moscow officials that its forces have ramped up efforts to push through Russia’s defensive lines in south-eastern Ukraine.
During his trip, Mr Cleverly also met children who were forcibly transferred to Russia and heard some survivors’ accounts at a centre supporting their return to Ukraine, the FCDO said.
“I was able to see for myself the true horrors and devastation of what Russia has wreaked on this sovereign state,” the Cabinet minister said in a statement.