Nato is to create a 4,000-strong "spearhead" high-readiness force that can be deployed rapidly in eastern Europe and the Baltic states to help protect member nations against potential Russian aggression, according to Nato officials.

Leaders from the 28 Nato countries are expected to approve the plan at the alliance's summit in Wales when the Ukraine crisis tops the agenda on Friday.

The Nato secretary-general, Anders Fogh Rasmussen, said the force, drawn on rotational basis from Nato allies, could be in action at "very, very short notice".

Rasmussen described it as a mixture of regular troops and special forces that could "travel light but strike hard". It would be supported by air and naval forces as needed...