President Joe Biden is sending about 2,000 troops from Fort Bragg, North Carolina, to Poland and Germany this week, and sending part of an infantry Stryker squadron of roughly 1,000 troops based in Germany to Romania, according to a senior administration official.
"The current situation demands that we reinforce Eastern flank," Pentagon spokesperson John Kirby said Wednesday.
Kirby added that the forces being sent to the region "are not going to fight in Ukraine," but were only being sent to shore up NATO's military forces.
Kirby said the Pentagon intended the military's presence to be temporary, not permanent deployments. But he did not rule out the possibility that more troops could be sent to the region in the weeks ahead.
When asked about the U.S. exit strategy and when the Pentagon would know their mission was accomplished, Kirby said that troops would be removed when NATO's eastern flank was "appropriately postured and able to defend itself."
He did not provide information on the troops' exact deployment or arrival dates.
The announcement comes the same day that a Spanish newspaper reported on a leaked text message that indicated the U.S. was open to negotiating the removal of some missiles from the region.
"We are open to addressing mutual security concerns," Kirby said Wednesday.
The moves come as Russia has amassed about 100,000 troops on the border of Ukraine in recent weeks, sparking fears of an invasion.
Russia denies having any such designs — and has laid out a series of demands it says will improve security in Europe, including a promise that NATO will not extend an invitation to Ukraine and a guarantee that the alliance will remove troops from Eastern Europe.
But the U.S. and the Western alliance have firmly rejected any concessions on Moscow's suggestions. Many of Russia's demands are nonstarters for NATO, creating a stalemate that many fear can only end in a war.
Last week, the Pentagon put 8,500 U.S. troops on "heightened alert" amid the heightened tensions. NATO allies have also begun moving military equipment toward Ukraine ahead of a potential invasion.
On Tuesday, Russian President Vladimir Putin said the U.S. and its allies had ignored Russia's top security demands that NATO not expand to Ukraine and other ex-Soviet nations, refrain from deploying offensive weapons near Russia and roll back its deployments to Eastern Europe.
In the past, Putin has expressed frustration with the Soviet breakup of some countries, like Belarus and Ukraine. According to an Associated Press analysis, Putin sees those countries as part of a historic Russian linguistic and Orthodox motherland.