Prime Minister Rishi Sunak is being urged to raise UK defence spending by a key eastern European ally.
Estonia, which borders Russia, has hosted British troops on rotation for years.
Its foreign minister Urmas Reinsalu told the BBC it was “vital” all Nato countries spend 3% of gross domestic product (GDP) on defence.
Mr Sunak has not matched a pledge, set by predecessor Liz Truss, to meet that target by 2030.
The new prime minister, who replaced Ms Truss in Downing Street this week, has previously described such targets as “arbitrary”.
However, he also said he believed in “investing in our armed forces” during his campaign to be Tory leader over the summer.
The UK currently spends just over 2% of GDP – a measure of the size of the economy – a year on defence.
‘We love UK soldiers’
Asked whether countries in the Nato defensive alliance, including the UK, should aim to spend 3% of GDP on defence, Mr Reinsalu replied: “Absolutely.”
He described Russia’s invasion of Ukraine as a “game-changer”.
“Autocrats are investing in weapons,” he told the BBC. “They believe in [the] power of arms.”
Nato estimates Estonia, which shares a 183-mile border with Russia and has a population of 1.3 million people, will spend 2.3% of its GDP on defence in 2022. Estonian ministers say they will raise this to 3% by 2024.
Nato countries committed in 2014 to spend at least 2% of GDP on defence by 2024. Only nine members expected to meet that target this year.
“To defend our values – the rules based order – we need also to invest to the weapons,” Mr Reinsalu said.
He also urged Britain not to cut troop numbers in Estonia, saying: “We love UK soldiers” and “we want more”.
A UK-led battlegroup has been based in Estonia since 2017, as part of a wider set of multinational Nato deployments in eastern Europe.
Around the time of the Russian invasion of Ukraine earlier this year, Britain’s presence was nearly doubled in the Baltic nation, with around 700 more soldiers.
However those additional troops are set to be withdrawn by the end of this year, leaving around 900 UK personnel in Estonia.
Discussions are said to be ongoing about plans for further British support that might better suit Estonia’s longer-term needs.
Mr Reinsalu said troop numbers should not be cut, but rather raised.
“I think [it is] very important not to give any mis-interpretative signals towards Russia,” he added.
He also called on the West to deliver more heavy weapons to Ukraine without “any political caveats”, adding the UK had set a “good example” in this area.
Chamberlain or Churchill?
In a call with President Volodymyr Zelensky, Mr Sunak promised to maintain British support to Ukraine but some major European countries, such as Germany and France, have faced accusations of being too slow to provide arms.
Mr Reinsalu said the West must be “determined” and that Kyiv must not be pressured into making concessions towards Russian President Vladimir Putin.
“Are we successors of Chamberlain or Churchill?” he asked, referring to two former British prime ministers.
Neville Chamberlain was associated with a policy of appeasement towards Hitler’s Nazi Germany in the 1930s.
When that policy failed, he was succeeded by the famous war-time leader Winston Churchill.
“We need to look towards a Ukrainian victory. Then we will not be ashamed to look ourselves [in the] mirror,” said Mr Reinsalu.
The UK Ministry of Defence said the additional British troops sent to Baltics countries earlier this year were “always a temporary deployment”.
A spokesperson added that forces will be held at high readiness in the UK for rapid reinforcement across the Baltic region.
“Our commitment to Nato and Estonia in response to Russia’s illegal invasion of Ukraine is absolute,” the spokesperson added.
Further details of UK defence spending will be set out in the autumn statement due on 17 November.