TALLINN, Estonia - Defense Secretary Ash Carter announced Tuesday that the US will spread about 250 tanks, armored vehicles and other military equipment across six European nations to help reassure NATO allies facing an array of threats from Russia and terrorist groups.

Each set of equipment would be enough to equip a military company or battalion, and would go on at least a temporary basis to Bulgaria, Estonia, Germany, Latvia, Lithuania, Poland, and Romania. Carter said the equipment could be moved around the region for training and military exercises, and would include Bradley fighting vehicles and self-propelled howitzer artillery guns.

But while the stated goal of the move is that American forces moving in and out of Europe will be better able to do training, it also would allow NATO nations to more quickly respond to any military crisis in the region.

Carter's announcement, made alongside defense ministers from Estonia, Latvia and Lithuania, comes a day after he announced that the US would be contributing weapons, aircraft and forces, including commandos, as needed for NATO's new rapid reaction force, to help Europe defend against potential Russian aggression from the east and the Islamic State and other violent extremists from the south.

The US, said Carter, is also going to work with NATO's cyber center, located in Estonia, to help allies develop cyber defense strategies and other protections against computer-based attacks.

The countries for the equipment storage were chosen based on their proximity to training ranges, to reduce the time and cost of transporting it for exercises.

The two-pronged US plan - with the placement of equipment in Europe and the commitment of resources for NATO's very high readiness task force - underscore America's commitment to helping allies counter the growing threats on Europe's eastern and southern fronts.

US and NATO allies have criticized Russia for its increasingly aggressive actions, including the annexation of Crimea and its backing of separatist troops on Ukraine's eastern border.

Under the plan to commit troops and resources if needed during a crisis, the US could see a temporary increase in American troops in Europe, although many could be reassigned from bases already in the region. No US troops or equipment will move immediately.

Carter said the US, if requested and approved, would be willing to provide intelligence and surveillance capabilities, special operations forces, logistics, transport aircraft, and a range of weapons support that could include bombers, fighters and ship-based missiles. It would not provide a large ground force.