NATO has agreed to 'maintain a continued presence in the east', on a rotational basis, NATO Secretary General Anders Fogh Rasmussen has said.
Speaking at a major NATO summit in Wales, Rasmussen said the plans shows "NATO protects all allies at all times," he adds.
"Should you even think of attacking one ally, you will face the whole alliance," Rasmussen added.
It comes after Baltic officials called for a permanent NATO presence in the region amid what they see as a threat from Russia.
Russia ambassador to EU Vladimir Chizhov said tension between the Baltics and Russia was 'artifically tense.'
As part of the deal, Great Britain could contribute 4,000 troops to the NATO rapid response force, British Prime Minister David Cameron said Friday.
The NATO rapid response force will be designed to meet new threats highlighted by the Ukraine crisis and Islamic militant gains in Syria and Iraq, the AFP news agency reports.
NATO was set up in 1949 to protect Western Europe from the Soviet Union, however, the collapse of the USSR created an illusion that traditional military threat to Europe was gone.
Cameron said that the alliance has to show that its Article 5 blanket security guarantee is still valid for all 28 NATO member states.
"As Russia tramples illegally over Ukraine, we must reassure our Eastern European members that we will always uphold our Article 5 commitments," Cameron told the second day of a NATO summit.
In order to do that, NATO "must be able to act more quickly," he said, hoping that the 28 allies would agree to set up a "spearhead force deployable anywhere in the world in just two to five days."
"If we can agree this, the UK will contribute 3,500 personnel," he added.
The two-day NATO summit has been billed as the most important since the end of the Cold War.