Britain on Monday announced major joint manoeuvres in Poland in October, part of a string of NATO exercises in the region aimed at reassuring eastern Europe members jittery over a resurgent Russia.

"I can announce today exercise Black Eagle, which will be a significant Polish and UK armoured exercise with over 350 British armoured and other vehicles and some 1,350 British personnel," British Defence Secretary Michael Fallon said in Warsaw.

The deployment will be the "largest British contribution to exercises in eastern Europe since 2008," he said at a joint press conference with British Foreign Secretary Philip Hammond and Poland's foreign and defence ministers.

Ex-communist NATO members have asked the alliance for permanent boots on the ground in the region amid the sharp escalation of fighting between Kiev government troops and pro-Russian rebels in eastern Ukraine.

Presidents from nine ex-communist NATO members met in Warsaw last week to hammer out a regional defence strategy to re-enforce its eastern frontier in preparation for a key summit in September.

The NATO summit is expected to focus largely on the fallout from the Ukraine crisis and Russia's annexation of that country's Crimean peninsula.

Senior NATO officials have said decisions on the possible permanent deployment of alliance forces throughout its eastern flank can be expected in September.

"The Russia-Ukraine conflict is Europe's most important security challenge since the end of the Cold War," Poland's President Bronislaw Komorowski has said.

"Strengthening NATO's eastern flank is fundamental."

NATO has already sent additional temporary rotations of air, sea and land forces to Poland and three small former Soviet-ruled Baltic states in response to the Ukraine crisis.

US President Barack Obama in June earmarked a billion dollars (741 million euros) in military funding for US allies on NATO's eastern border.