Troops were set to hit the ground in Poland Tuesday as Warsaw kicks off its largest-ever joint military exercises with its NATO allies, aimed at shoring up regional security amid the West's worst standoff with Russia since the end of the Cold War.

The two-week long Anaconda manoeuvres are aimed at "checking the alliance's ability to defend its eastern flank," Polish Defence Minister Antoni Macierewicz said at opening ceremonies in Warsaw the previous day.

The move comes a month ahead of a landmark NATO summit in Warsaw set to seal its largest revamp since the Cold War by deploying more troop rotations to eastern European members spooked by Russia's 2014 annexation of Crimea from Ukraine.

Moscow fiercely opposes NATO moves to reinforce its eastern flank, billed by the alliance as part of its "deterance and dialogue" strategy.

The latest in a string of NATO manoeuvres in the region, Anaconda involves some 31,000 soldiers from 24 alliance states, including 14,000 from the US, 12,000 Poles and 1,000 from Britain as well as personnel from former-Soviet "Partnership for Peace" states like Ukraine and heavy equipment deployments.

- Troop rotations -

NATO has been careful to reassure Moscow ahead of the July summit, with its Secretary General Jens Stoltenberg insisting "the Cold War is history and we want it to stay that way."

Russia has long objected to NATO's expansion in its Soviet-era backyard and in 1997 NATO formally agreed not to install permanent bases in former Warsaw Pact states.

But some European security analysts question whether NATO's current strategy, based on the deployment of rotational rather than permanent forces, can really secure its eastern flank.

"When push comes to shove, how long will it really take to mobilise at break-neck speed troops in the possibility of a threat of an attack?" Carnegie Group analyst Judy Dempsey said in an interview with AFP.

"If it (NATO) is not going to permanently deploy troops, then it really should speed up infrastructure to move troops there (to the eastern flank) quickly."

Since the Ukraine conflict, NATO has established a high-speed "spearhead" response force, complete with forward command and logistic centres in its eastern members so it can deploy much more rapidly.

But Dempsey, editor in chief of the think tank's "Strategic Europe" section, questions the usefulness of the relatively small units in the face of "huge conventional forces on the other side."

Moscow has significantly stepped up its presence in the Baltic Sea area and its jets regularly violate the airspace of smaller ex-Soviet NATO allies like Estonia. In April, they even buzzed a US naval destroyer.

According to Dempsey, NATO's ongoing "exercises are tiny compared to what Russia is doing."

"Russian exercises are sophisticated, they're big, they're intimidating and look what they're doing in Kaliningrad," she said, referring to Moscow's manoeuvres in the Russian enclave sandwiched between NATO members Poland and Lithuania.

"It's like a warning to NATO: 'don't forget, we're right inside NATO territory'."

- 'Test of wills' -

While NATO cut all practical cooperation with Moscow following Russia's Ukraine intervention, the US-led alliance vowed to hold formal talks with the Russians before the July 8-9 summit.

But just last month Moscow and Washington accused each other of mounting an aggressive military presence in northern Europe as the United States broke ground on a missile shield in NATO allies Poland and Romania.

Russia has vowed to "end threats" posed by the system, despite US assurances that it is intended to ward of potential attacks by so-called "rogue" states in the Middle East.

The Kremlin said it would set up three new divisions in the west and south of the country by the end of the year to counter NATO forces close to its border.

Describing the the confrontation as "a test of wills", Dempsey believes that ultimately Moscow's sabre rattling is aimed at stopping NATO from encroaching even further into its backyard.

"Of course Russia politically and rhetorically worries about the (NATO) exercises, but at the end of the day, what Moscow really worries about is the future expansion of NATO -- as in think of Georgia and Ukraine," she said, referring to two ex-Soviet republics now keen to join the Western alliance.