Nato needs a rapidly deployable force able to demonstrate to Russia an attack on any ally is an attack on the whole alliance, David Cameron said today.
Speaking after a meeting with Secretary General Anders Fogh Rasmussen and Supreme Allied Commander in Europe Philip Breedlove at the alliance headquarters in Belgium, the Prime Minister said the Nato summit in Wales in September would be a key moment.
The meeting came amid a visit by the Prime Minister to mark the 100th anniversary of the outbreak of World War One.
In a statement alongside the secretary general after the meeting, Mr Cameron said: "Since Russia destabilised Ukraine and illegally annexed Crimea, Nato's response has focused on reassuring our eastern allies and deterring Russian aggression elsewhere. Every ally has contributed to this response, whether with ships, aircraft or troops.
"At the Nato summit we must agree how we can sustain such a robust presence in eastern Europe in the months ahead.
"I support General Breedlove's plans to reinforce Nato's headquarters in Poland, to preposition equipment and supplies and to schedule a series of exercises that will make clear we will not be intimidated by Russia's aggressive behaviour.
"We must also use the summit to ensure Nato is prepared to respond swiftly to any threat against any ally, including with little warning.
"That means a multi-national, high readiness force that can deploy quickly on exercises in the territory of an ally that feels threatened.
"This would provide clear reassurance for any vulnerable ally and make clear to any aggressor that an attack on one would be an attack on all."
Mr Rasmussen said: "We are at a crucial point in history.
"As we remember the devastation of World War One, our peace and security are once again being tested, now by Russia's aggression against Ukraine, and the criminal downing of Flight MH17 has made clear a conflict in one part of Europe can have tragic consequences around the world.
"Nato stands determined to defend all allies against any threat. We have taken immediate measures to strengthen our collective defence in the air, at sea, on land."
Mr Cameron also called for an Alliance Charter on the treatment of service personnel to be agreed, modelled on Britain's Armed Forces Covenant.
He said: "This would be reinforced by a new approach to share more systematically across Nato the best practice on the treatment of armed forces - medical care, how we support our injured personnel, the way we look after bereaved families. These will all be priorities for this work.
"Today people around the world commemorate all those who gave their lives 100 years ago in the hope of freedom and peace.
"Today, it is also important to remember it is Nato which has provided the bedrock of security and peace across Europe for the past 65 years.
"We must ensure Nato continues to foster global peace and security in the coming years and that will be at the heart of our agenda at the Nato summit in Wales next month."