Europe must remain united in the face of the threat from Russia, David Cameron has warned amid fears Britain's withdrawal from the EU will weaken its resolve to stand up to Vladimir Putin,

Speaking at the Nato summit in Warsaw, the Prime Minister said there had to be a "hard-headed dialogue" with Moscow to prevent any "misunderstanding or miscalculation" leading to conflict.

At the same time he stressed that both the EU and the alliance needed to be prepared to stand firm in face of any fresh aggression by Russia following its annexation of Crimea from Ukraine in 2014.

His comments came after President Francois Hollande said France regarded Russia as a partner, "not a threat" and that Nato had no role in determining what Europe's relations with Moscow should be.

Mr Cameron told a news conference: "Of course we must have a dialogue with Russia - there are many issues we need to discuss with Russia, not least the situation in Syria.

"But there was a very strong consensus that we need to have that dialogue from a position of unity and strength over the issue of Ukraine. Boundaries are being redrawn in Europe by force by one power and Europe and Nato must be strong against that.

"We are not seeking confrontation with Russia. We are working to prevent it so we will continue to pursue a twin-track approach of deterrence and dialogue.

"We must engage in a hard-headed dialogue with Russia to avoid misunderstanding or miscalculation."

After Nato leaders confirmed plans on Friday to station four new battalions numbering around 4,000 troops - including 650 British personnel - in eastern Europe, Mr Cameron said the Nato-Russia council would meet next week for the first time in many months in an attempt to ensure the deployments did not create new friction.

The Prime Minister also confirmed that Britain is to send an additional 50 troops to Afghanistan in a training and mentoring role while extending the mission of the 450 already there to help shore up the Afghan security forces.

It following an announcement by President Barack Obama that the remaining 8,400 US troops in the country are to stay on for the rest of his presidency in the face of the worsening security situation.