Backed by an increase in U.S. military spending, Nato is planning its biggest build-up in eastern Europe since the Cold War to deter Russia but will reject Polish demands for permanent bases.

Worried since Russia's seizure of Crimea that Moscow could rapidly invade Poland or the Baltic states, the Western military alliance wants to bolster defences on its eastern flank without provoking the Kremlin by stationing large forces permanently.

Nato defence ministers will next week begin outlining plans for a complex web of small eastern outposts, forces on rotation, regular war games and warehoused equipment ready for a rapid response force. That force includes air, maritime and special operations units of up to 40,000 personnel.

The allies are also expected to offer Moscow a renewed dialogue in the NATO-Russia Council, which has not met since 2014, about improved military transparency to avoid surprise events and misunderstandings, a senior NATO diplomat said.

US plans for a four-fold increase in military spending in Europe to $3.4 billion in 2017 are central to the strategy, which has been shaped in response to Russia's annexation of Crimea from Ukraine in 2014.

The plans are welcomed by Nato whose chief, Secretary General Jens Stoltenberg, says it will mean "more troops in the eastern part of the alliance ... the pre-positioning of equipment, tanks, armoured vehicles ... more exercises and more investment in infrastructure".

Such moves will reinforce the message from US President Barack Obama, in a speech he delivered in Estonia in 2014, that Nato will help ensure the independence of the three Baltic states, which for decades were part of the Soviet Union.

Lithuanian Defence Minister Juozas Olekas has described Russia as a threat but many European countries in the North Atlantic Treaty Organisation are wary of upsetting the continent's biggest energy supplier.

With such concerns paramount, diplomats and officials say Nato will not back requests for permanent bases by Poland, which has a history of fraught relations with Russia.

"I am a great proponent of strong deterrents and to improve our resilience, but I do think that the best way to do it is to do it on a rotational basis," Dutch Defence Minister Jeanine Hennis-Plasschaert said.

Stoltenberg has also said he will not be "dragged into an arms race".

Russia has made clear it would regard any moves to bring Nato infrastructure closer to its borders a threat and the Kremlin has warned it would take "reciprocal steps."

Western powers' relations with Russia have deteriorated over the almost two-year-old conflict in Ukraine but the West also need Russia's help in dealing with terrorism and the battle against Islamic State in Syria and Iraq.

If approved by Congress, Washington says one U.S. armoured brigade combat team's vehicles and equipment will be stored in warehouses in Germany and the east, from Bulgaria to Estonia.

Moving equipment nearer a potential front is seen as crucial to be able to combat quickly Russia's surface-to-air missile batteries and anti-ship missiles in its Kaliningrad exclave that can prevent forces from entering or moving across air, land and sea.

A study by the RAND Corporation, a U.S. defence think tank, found that Russia could overrun the Baltics states of Estonia, Latvia and Lithuania within three days, leaving Nato and the United States no good options to respond.