David Cameron and Defence Secretary Michael Fallon are to hold talks with key western allies amid growing tension with Russia over President Vladimir Putin's military intervention in Syria.
The Prime Minister will hold a working dinner with German chancellor Angela Merkel at Chequers after first meeting Estonian prime minister Taavi Roivas.
Their talks come after Mr Fallon announced plans for the deployment of around 100 British troops in to the Baltic States of Latvia, Lithuania and Estonia as part of a "more persistent presence" by Nato forces in eastern Europe.
At a meeting on Thursday of Nato defence ministers in Brussels, Mr Fallon said the move was part of a plan to ensure the alliance was able to respond to any further "provocation and aggression" on the part of Moscow.
The Defence Secretary is holding further meetings in London with his US and German counterparts - Ash Carter and Ursula von der Leyen.
At the meeting in Brussels, Nato ministers denounced Russia's intervention in Syria as "not helpful" and condemned the "unacceptable" violation of Turkish airspace by Russia war planes engaged in attacking rebel forces.
The Russians insist they are targeting Islamic State (IS) extremists - also referred to as Isil or Isis - but Western sources say they have largely hit mainstream opposition forces.
They believe the air strikes are primarily designed to prop up President Bashar Assad, who Britain, the US and other Western countries insist must go as part of any political settlement of Syria's four-year civil war.
Moscow's action has also rekindled fears among former Soviet bloc states like the Baltics that they could be the next targets of Russian aggression as Mr Putin seeks to re-assert himself on the world stage.
Nato secretary general Jens Stoltenberg sought to address such concerns, announcing plans had been finalised for a response force of up to 40,000 - twice the current size - and new Nato headquarters offices in Hungary and Slovakia.
"All of this sends a clear message to all Nato citizens. Nato will defend you, Nato is on the ground, Nato is ready," he said.
Earlier this week Mr Cameron acknowledged that despite the current difficulties, the West would have to try to find ways of working with the Russians if there was to be a political re-solution to the crisis in Syria.
The Prime Minister is also expected to use his meetings with Mrs Merkel and Mr Roivas to discuss his ongoing effort to re-negotiate the terms of Britain's membership of the European Union.