President Joe Biden is ordering 2,000 U.S.-based troops to Poland and Germany and shifting 1,000 more from Germany to Romania, demonstrating to both allies and foes America’s commitment to NATO’s eastern flank amid fears of a Russian invasion of Ukraine, the Pentagon said Wednesday.

Russia fired back with a sharply worded objection, calling the deployments unfounded and “destructive.”

Russian President Vladimir Putin also had a new telephone exchange with British Prime Minister Boris Johnson. But readouts from both governments showed no progress, with Putin saying the West was giving no ground on Russia’s security concerns and Johnson expressing deep concern about Russia’s “hostile activity” on the Ukrainian border, referring to Putin’s buildup of 100,000 troops there.

The Biden administration is aiming to demonstrate U.S. resolve without undermining efforts to find a diplomatic solution to the crisis. Biden notably has not sent military reinforcements to the three Baltic countries on NATO’s eastern flank — Estonia, Latvia and Lithuania — that are former states of the Soviet Union.

No U.S. troops are being sent to Ukraine, and White House press secretary Jen Psaki on Wednesday said the administration has stopped calling a Russian invasion “imminent,” because that word implies Washington knows Putin has made a decision to invade. Officials say Putin’s intentions remain unclear.

However, increasing U.S. troop levels in Eastern Europe is exactly what Putin has said he finds intolerable, along with the prospect of Ukraine joining NATO. The U.S. already has several thousand troops in Poland, and Romania is host to a NATO missile defense system that Russia considers a threat. The U.S. presence in the region has increased since 2014 when Russia made its first invasion of Ukraine.

Pentagon press secretary John Kirby said the soon-to-deploy U.S. forces are intended to temporarily bolster U.S. and allied defensive positions.

“These are not permanent moves,” he said, stressing that the purpose is to reassure allies. Kirby said Russia had continued its buildup, even in the previous 24 hours, despite U.S. urgings that it deescalate.

In Moscow, a senior official said the U.S. movements will complicate the crisis.

“The unfounded destructive steps will only fuel military tensions and narrow the field for political decisions,” Deputy Foreign Minister Alexander Grushko said in remarks carried by the Interfax news agency.

Ukraine’s Foreign Minister Dmytro Kuleba again played down fears of a Russian attack in a call with reporters but said that if Russia makes moves that could signal an imminent invasion Ukraine would react as necessary.

Of the 2,000 U.S. troops newly deploying from Fort Bragg, North Carolina, about 1,700 are members of the 82nd Airborne Division infantry brigade, who will go to Poland. The other 300 are with the 18th Airborne Corps and will go to Germany as what the Pentagon called a “joint task force-capable headquarters.”

Poland’s Defense Minister Mariusz Blaszczak wrote on Twitter that the deployment to his country is “a strong signal of solidarity in response to the situation in Ukraine.”

The 1,000 U.S. troops going to Romania are members of the 2nd Cavalry Regiment based at Vilseck, Germany. They will augment about 900 already in Romania, Kirby said.

The cavalry deployment’s purpose is to “deter aggression and enhance our defensive capabilities in frontline allied states during this period of elevated risk,” the Pentagon said in a separate written statement.

“It’s important that we send a strong signal to Mr. Putin and to the world” of the U.S commitment to NATO, Kirby said.

He said France has decided it, too, will send troop reinforcements to Romania under NATO command, and he noted that a number of other European NATO countries are considering adding forces on NATO’s eastern flank. Biden and French President Emmanuel Macron touched base in a phone call Wednesday night.

NATO has been beefing up its defenses around allies in Eastern Europe since late last year. Denmark, for example, said it was sending a frigate and F-16 warplanes to Lithuania, and Spain was sending four fighter jets to Bulgaria and three ships to the Black Sea to join NATO naval forces. The Netherlands plans to send two F-35 fighter aircraft to Bulgaria in April and is putting a ship and land-based units on standby for NATO’s Response Force.

Biden has said he will not put American troops in Ukraine to fight any Russian incursion, although the United States is supplying Ukraine with weapons to defend itself and seeking to reassure allies in Eastern Europe that Washington will fulfill its treaty obligation to defend them in the event they are attacked.

Ukraine is not a NATO member, and therefore the U.S. has no treaty obligation to come to its defense.

The military moves come amid stalled talks with Russia over its buildup at Ukraine’s borders. And they underscore growing fears across Europe that Russian President Putin is poised to invade Ukraine. Smaller NATO countries on the alliance’s eastern flank worry they could be next.

The Pentagon also has put about 8,500 U.S.-based troops on higher alert for possible deployment to Europe as additional reassurance to allies, and officials have indicated the possibility that additional units could be placed on higher alert soon. The U.S. already has between 75,000 and 80,000 troops in Europe as permanently stationed forces and as part of regular rotations in places such as Poland.

Washington and Moscow have been at loggerheads over Ukraine, with little sign of a diplomatic path forward. However, Kirby on Wednesday confirmed the validity of a document reported by a Spanish newspaper that indicated the United States could be willing to enter into an agreement with Russia to ease tensions over missile deployments in Europe if Moscow steps back from the brink in Ukraine.

The daily El Pais published two documents that Kirby confirmed were written replies from the United States and NATO last week to Russia’s proposals for a new security arrangement in Europe. The U.S. State department declined to comment on them.

In reference to the second document, NATO said that it never comments on “alleged leaks.” But the text closely reflects statements made to the media last week by NATO Secretary-General Jens Stoltenberg as he laid out the 30-nation military organization’s position on Russia’s demands.

The U.S. document, marked as a confidential “non-paper,” said the United States would be willing to discuss in consultation with its NATO partners “a transparency mechanism to confirm the absences of Tomahawk cruise missiles at Aegis Ashore sites in Romania and Poland.”

That would happen on condition that Russia “offers reciprocal transparency measures on two ground-launched missiles bases of our choosing in Russia.”

Aegis Ashore is a system for defending against short- or intermediate-range missiles. Russia argues the site in Romania could be easily adapted to fire cruise missiles instead of interceptors, a claim that Washington has denied.

In his first public remarks on the standoff in more than a month, Putin on Tuesday accused the U.S. and its allies of ignoring Russia’s central security demands but said that Moscow is willing to keep talking.

Russia invaded Georgia in 2008, and in 2014 annexed Ukraine’s Crimean Peninsula and provided military support for a pro-Russian separatist movement in eastern Ukraine. Around 14,000 people have been killed in the conflict in eastern Ukraine.