President Biden will send 31 M1 Abrams tanks to Ukraine, matching a German announcement to immediately provide Leopard tanks that Kyiv says are essential in their fight against Russia.

The Abrams tanks are not expected to reach the battlefield for months related to the time needed to procure the tanks and carry out the training necessary for Ukrainian forces, senior administration officials told reporters Wednesday.

The decision to provide the Abrams tanks marks a stunning reversal for the Biden administration, which had previously argued they would be of little benefit to Ukraine.

But the decision to send the tanks helped get Germany to move forward with a separate effort to provide Leopard tanks to Ukraine, which the U.S. had seen as benefitting Kyiv.

German Chancellor Olaf Scholz announced Wednesday that Berlin would send Leopard tanks to Ukraine and allow for other European nations to also send to Kyiv the German-made tanks.

“Today’s announcement really was the product of good diplomatic conversations as part of our regular and ongoing close consultations with allies and partners on security assistance to Ukraine,” a senior administration official said. “Certainly very appreciative of Chancellor Scholz’s announcement today.”

Ukraine lobbied hard for U.S., Germany and other countries to supply the tanks, which it said would be critical to a spring counteroffensive against Moscow.

“So the tank coalition is formed. Everyone who doubted this could ever happen sees now: for Ukraine and partners impossible is nothing,” Ukrainian Foreign Minister Dymtro Kuleba tweeted.

A senior administration official, responding to a question over whether the delivery of Abrams was a precondition for the Germans to greenlight Leopards, said Biden and Sholz spoke several times by phone over the past month and that the tank discussion was part of an “iterative conversation” between the U.S. and Germany.

“We have closely coordinated our security assistance with allies and partners throughout the conflict, including Germany,” the official said.

Biden spoke Wednesday morning with Sholz, French President Emanuel Macron and British Prime Minister Rishi Sumak, officials said.

A senior administration official said the U.S. expects other nations to announce contributions of additional armored capability, including some that will be readily available for use on the battlefield in the coming weeks and months. 

The administration expects that Russian President Vladimir Putin will push for the Russian military to go on another offensive as the weather improves, another senior administration official said. The tanks decision is meant to help give the Ukrainians the “the ability to retake, to reclaim their sovereign territory and that means everything that is recognized by international borders.”

The British Ministry of Defense said in a recent intelligence assessment that Ukraine has liberated around 54 percent of the maximum amount of extra territory Russia seized since it launched its full-scale invasion on Feb. 24.

Russia still controls around 18 percent of internationally recognized areas of Ukraine, including the eastern region of Ukraine, called the Donbas, and the Crimean peninsula, which Moscow seized in 2014. Their annexations have been rejected by the U.S. and other international partners. 

Ukrainian President Volodymyr Zelensky has said the full liberation of Ukrainian territory, and in particular Crimea, is necessary for any peace talks with Russia. 

The Biden administration has been careful in offering military support to Ukraine, wary of Putin threats to use nuclear weapons.

Russia’s ambassador to Germany, Sergei Nechaev, reportedly said in a statement Wednesday that Germany’s decision to approve the delivery of Leopards is “extremely dangerous” and takes the conflict “to a new level of confrontation.” 

Western support of advanced military capabilities is viewed as essential for Ukrainians to mount a counter offensive that could threaten Russia’s holding of the Crimean peninsula.

The senior administration official, responding to a question of whether the administration supports Ukraine retaking territory in the Donbas and Crimea, said that the U.S. does not “tell the Ukrainians where to strike, where to attack, where to conduct offensive operations.”

“Crimea is Ukraine. We’ve never recognized the illegal annexation of Crimea,” the official continued. “But where the Ukrainians decide to go and how they decide to conduct operations in their country, those are their decisions to make.” 

It is expected to take months before the Abrams reach the battlefield. Training of Ukrainian forces for operating and maintaining the tanks is expected to take place outside of Ukraine, the officials said. 

A senior administration official described the coordination on tanks for Ukraine as “an impressive display of unity nearly a year into the conflict,” underscoring Biden’s focus on coordination with allies and partners. 

“The President has been extremely focused on the importance of alliance-unity, of Trans-Atlantic unity, and we have tried to make that a hallmark of everything that we have done for Ukraine throughout the 11 months of this conflict.”