NEWPORT, Britain - NATO leaders at their Wales Summit on Friday agreed on a Readiness Action Plan to strengthen the bloc's collective defense and to ensure the alliance is ready to deal with any challenge, NATO Secretary General Anders Fogh Rasmussen announced Friday.

The NATO Allies face a security environment which is more unpredictable than ever, including Russia's "aggression" against Ukraine, violent extremism in the Middle East and instability in North Africa, Rasmussen said at a press conference on the second day of the NATO summit in Newport, southeast Wales of Britain.

NATO leaders at their meeting agreed to maintain a "continuous presence" and activity in the air, on land and at sea in the eastern part of the Alliance, on a rotational basis, the NATO chief said.

"In these turbulent times NATO must be prepared to undertake the full range of missions and to defend Allies against the full range of threats," he added.

They also agreed to create a spearhead unit within the NATO Response Force which would be a very high readiness force able to deploy at very short notice.

"This spearhead will include several thousand land troops ready to deploy within a few days with air, sea and Special Forces support," Rasmussen told the press conference.