The decision to draft contingency plans for the former Soviet states of Estonia, Latvia and Lithuania was taken secretly earlier this year at the urging of the United States and Germany at NATO headquarters, ending years of division within the alliance over how to view Russia, the Guardian said.
In parallel talks with Warsaw, it said, Washington offered to beef up Polish security against Russia by deploying special naval forces to the Baltic ports of Gdańsk and Gdynia, putting F-16 fighter aircraft in Poland and rotating C-130 Hercules transport planes into Poland from US bases in Germany.
The details were from 250,000 diplomatic cables obtained by the website WikiLeaks that are being made public.
NATO leaders were understood to have quietly endorsed the new strategy to defend vulnerable parts of eastern Europe at a summit in Lisbon last month, the Guardian said.
In Lisbon, NATO and Russia agreed to cooperate on missile defence and other security issues, and hailed a new start in relations strained since Russia's military intervention in Georgia in 2008. US President Barack Obama has a policy of "resetting" relations with Moscow.
But the WikiLeaks cables point to the underlying tension in the relationship between the former Cold War adversaries.
The plan entailed grouping the Baltic states with Poland in a new regional defence scheme, codenamed Eagle Guardian, said the paper.
Poland, the Baltic states and others were rattled by Russia's brief war against Georgia and have been irked by large-scale Russian army exercises in Belarus and by Moscow's new military doctrine that sees NATO expansion as a threat.
The Guardian said nine NATO divisions - US, British, German and Polish - had been identified for combat operations in the event of aggression against Poland or the Baltic states.
North Polish and German ports had been listed to receive naval assault forces and British and US warships, the paper said.
The first NATO exercises under the plan were to take place in the Baltic next year, it quoted informed sources as saying.
Germany and other Western European countries had previously opposed drawing up plans to defend the Baltic states, anxious to avoid upsetting Russia.
Earlier this year, the United States started rotating US army Patriot missiles into Poland.
But the secret cables exposed the Patriots' value as purely symbolic. The Patriot battery was for training purposes, and was neither operational nor armed with missiles, said the Guardian.
(EurActiv with Reuters.)