Riga (AFP) - The United States on Monday delivered more than 100 pieces of military equipment to vulnerable NATO-allied Baltic states in a move designed to provide them with the ability to deter potential Russian threats.

The deliveries are intended to "demonstrate resolve to President (Vladimir) Putin and Russia that collectively we can come together," US Major General John R. O'Connor told AFP as he oversaw the delivery of the equipment in the port of Riga.

The delivery included Abrams tanks, Bradley fighting vehicles, Scout Humvees as well as support equipment and O'Connor said the armour would stay "for as long as required to deter Russian aggression".

The three former Soviet-ruled Baltic states of Estonia, Latvia and Lithuania, all NATO and European Union members since 2004, have very little miliary hardware of their own.

Moscow's annexation of Crimea last year and its meddling in the conflict in eastern Ukraine have galvanised NATO and focused particular attention on its vulnerable Baltic members.

A series of military manoeuvres by Russia in the Baltic area has stoked deep concern that the Kremlin could try to destabilise the countries that were in its orbit during Soviet times.

NATO is countering Russia's moves by boosting defences on Europe's eastern flank with a spearhead force of 5,000 troops and command centres in six formerly communist members of the alliance, including the three Baltic states and Bulgaria, Poland and Romania.

"What we're demonstrating is a unified front from the north to the south," O'Connor said.

Lithuanian President Dalia Grybauskaite warned last week that Baltic states must be ready to repel any invasion on their own for "at least 72 hours" before NATO allies could send in help.