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”.