Around 750 US Army tanks and other vehicles and military equipment are already in Latvia for the so-called "Operation Atlantic Resolve" exercises with NATO partners.

The drills will continue for three months, though a US military source quoted by various media outlets argues the equipment will remain in the region even after this period.

The latest exercises, will will be carried out across Lithuania, Latvia and Estonia, are aimed at demonstrating "resolve to President [Vladimir] Putin and Russia that collectively we can come together," DW quotes US General John O'Connor as saying.

They are also a means of reassuring NATO allies of the alliance's support for those Eastern European states concerned over what they describe as a "threat" coming from Russia.

Russian agency TASS quotes O'Connor as saying the heavy machinery will remain “for as long as required to deter Russian aggression.”

NATO decided last year to bolster its eastern flank increasing the number of troops and drills there and voted this February to set up coordination centers in six Eastern European states, including Bulgaria.

Also last year, Ukrainian President Petro Poroshenko cited a conversation between Putin and EU Commission ex-President Jose Manuel Barroso in which the former reportedly warned his troops could reach NATO member states "within two days".