Some of the tanks and vehicles - enough to equip an armored brigade - could be placed in Poland, Romania or the Baltic states, Lieutenant-General Ben Hodges, commander of the U.S. Army in Europe, said in a telephone interview with Reuters from Wiesbaden, Germany.

Hodges said a proposal to have a U.S. brigade rotate to Europe was first made two years ago, before the crisis over Russia's annexation of Ukraine's Crimea region.

That meant a U.S. armored unit was already in the pipeline to come to Europe earlier this year, when it was needed as part of U.S. measures to reassure eastern European allies in response to the Ukraine crisis, he said.

Hodges said he saw a risk that pro-Russian separatists in eastern Ukraine might launch a new offensive in the spring. Russia denies any aggressive activity.

Hodges said he expected the U.S. measures, which include an expanded exercise program, to go on throughout 2015 and into 2016.

Keeping enough equipment in Europe for a U.S. armored brigade avoids the need for troops coming from the United States for exercises to bring their own kit.

It also means the equipment is there if the United States needed to reinforce eastern Europe quickly in an emergency.

"By the end of ... 2015, we will have gotten all the equipment for a heavy brigade, that means three battalions plus a reconnaissance squadron, the artillery headquarters, engineers, and it will stay in Europe," Hodges said.

"You are talking about 150-ish, maybe 160 M1 tanks, M2 Bradley fighting vehicles, 24 self-propelled howitzers."

No decision has yet been taken on where the armored vehicles will be kept.

Hodges said he expected at least a third of it to remain at U.S. training centers in Germany. The United States may consider distributing some of the equipment to a Baltic country, Poland or Romania if it made strategic sense and if that country wanted it kept there.

The United States has sharply cut its forces in Europe since the Cold War. It now has about 30,000 troops there plus a similar number of Air Force, Navy and Marine personnel, Hodges said.

Despite budgetary pressures in the United States, Hodges said he hoped U.S. soldiers and bases in Europe would remain at their current levels for now.