A Moscow-friendly Greece could paralyse NATO's ability to react to Russian aggression, former US national security adviser Zbigniew Brzezinski warned Wednesday.

Athens could use its veto to slow the alliance's response if Russia set its sights on its Baltic member states, he told Poland's Dziennik Gazeta Prawna.

The Cold War-era hawk, who worked for president Jimmy Carter from 1977 to 1981, said Poland too "could be a target" after Russia's annexation of Crimea last year, as well as former Soviet states such as Moldova, Georgia and oil-rich Azerbaijan.

NATO's Article 5 commits the 28-member alliance to respond collectively if a member is attacked, he said.

"But NATO is bound by the principle of unanimity," Polish-born Brzezinski said, warning that the alliance "could be paralysed for some time...namely by Greece, which is a friend of Russia and wields veto power."

Greece's radical left government is cultivating ties with Russia amid Athens' scramble to avoid bankruptcy.

Greek Prime Minister Alexis Tsipras will meet Russian President Vladimir Putin on April 8 in Moscow before returning for an annual Victory Day parade in May.

Greek officials have openly floated the prospect of Athens turning to Russia or China for help if loan talks with the EU end in failure.

Since it sliced Crimea away from Ukraine last year, Russia has engaged in sabre rattling in the Baltic region.

Earlier this year, Brzezinski urged the US and its allies to deploy troops to Baltic states to deter Russia from staging a possible incursion into the formerly Soviet-ruled countries.

NATO is deploying more aircraft, ships and personnel for exercises on its eastern flank, which lay behind the Iron Curtain a quarter of a century ago.

NATO has also created a force of 5,000 troops capable of rapid deployment and will establish command centres in the Baltic states, Bulgaria, Poland and Romania by 2016.