Biden approves sending 31 Abrams tanks to Ukraine

In a major increase of U.S. support to Ukraine, President Joe Biden has signed off on sending 31 M1 Abrams tanks to the war-torn country as concerns mount over a new Russian offensive this spring.

"Secretary [Lloyd] Austin has recommended this step because it will enhance the Ukraine's capacity to defend its territory and achieve its strategic objectives," Biden said on Wednesday in remarks from the White House's Roosevelt Room, flanked by Austin, the defense secretary, and Secretary of State Antony Blinken.

Ukraine's President Volodymyr Zelenskyy has repeatedly appealed for more tanks, with a harsh winter and the one-year anniversary of Russia's invasion approaching.

The political maneuvering had muddled Ukraine's plea while Russia is thought to be preparing for a spring offensive.

For weeks, Pentagon officials said publicly that the Abrams tanks weren't suited for the fight in Ukraine, including because of the fuel they need to operate. But officials also did not rule out the vehicles as a potential long-term possibility.

The U.S. transfer of Abrams tanks seemingly spurred Germany to authorize the transfer of German-made Leopard 2s to Ukraine -- and allow the 12 NATO countries that have Leopard 2s to send them to Ukraine, with the most vocal of those countries being Poland.

"We remain united and determined as ever in our conviction and our cause," Biden said at the White House. "These tanks are further evidence of our enduring, unflagging commitment to Ukraine and our confidence in the skill of the Ukrainian forces. As I told President Zelenskyy when he was here ... in December: 'We're with you for as long as it takes, Mr. President.'"

Thirty-one Abrams tanks is a specific number, a U.S. official told reporters in a conference call earlier Wednesday, as it constitutes one Ukrainian tank battalion. "So we are specifically meeting that requirement."

Biden said that the U.S. is also pledging to train Ukrainians so they are prepared to integrate the Abram tanks into their defenses, though U.S. officials separately acknowledged the new vehicles won't arrive for months.

The transfer of European tanks is set to be more expedient.

"The Abrams tanks are the most capable tanks in the world. They're also extremely complex to operate and maintain, so we're also giving Ukraine the parts and equipment necessary to effectively sustain these tanks on the battlefield. And we'll begin to train the Ukrainian troops on these issues of sustainment, logistics and maintenance as soon as possible," Biden said.

Administration officials had confirmed to ABC News on Tuesday that they were considering sending the Abrams tanks to Ukraine under the Ukraine Security Assistance Initiative. That means the U.S. will arrange for the contracting of the tanks with their manufacturer, so the vehicles will not be able to be fielded for quite some time -- possibly more than a year.

On Wednesday, Biden confirmed the extended timeline, which government officials had said could take "months, as opposed to weeks."

"Delivering these tanks to the field is going to take time," the president said.

Early Wednesday, Germany confirmed it will supply Ukraine with Leopard 2 tanks and approve requests by dozens of other countries to do the same. The U.K. has also committed 12 of its own Challenger 2 battle tanks, and Poland has asked Germany for permission to send the Leopards it has in stock.

The president said he spoke Wednesday morning about the war with French President Emmanuel Macron, German Chancellor Olaf Scholz, Italian Prime Minister Giorgia Meloni and U.K. Prime Minister Rishi Sunak.

"I'm grateful to Chancellor Scholz for providing German Leopard 2 tanks and will lead an effort to organize the European contribution of two tank battalions for Ukraine," Biden said. "Germany has really stepped up. The chancellor has been a strong, strong voice for unity, a close friend and for the level of effort we're gonna continue."

Asked about the timing of this decision and whether Germany "forced you to change your mind" about sending tanks, which the Pentagon was initially against, Biden defended the move as a coordinated decision.

"Germany didn't force me to change your mind. We wanted to make sure we were all together. That's what we were going to do all along and that's what we're doing right now," he said.

Still, the commitment of tanks -- which a Ukrainian official had told ABC News could number about 100 Leopard 2s -- falls far short of the 300 battle tanks that Zelenskyy has said he needs.

U.S. officials argued on Wednesday that the new shipment of tanks highlights the unity among all allies working to support Ukraine, minimizing the disagreement between the U.S. and Germany on the usefulness of the Abrams vehicles.

Zelenskyy reacted to the tank commitments in a new SkyNews interview. "I would like to say thank you to Germany, to Britain and to the United States that they made this decision," he said.

Russia reacts: 'Burn up ... like any other'

The Kremlin has downplayed the new supply of tanks, with spokesman Dmitry Peskov saying in his daily briefing on Wednesday that "to supply U.S.-made Abrams tanks to Ukraine won't work, as its initiators overestimate the potential of Ukrainian servicemen."

"I am sure that many specialists overestimate the absurdity of this idea. Simply because it's a rather bad plan in its technological aspects and, most importantly, there is an obvious overestimation of the potential it could add to the Ukrainian Armed Forces. This is yet another profound misconception," he added.

"We have repeatedly said that these tanks will burn up just like any other," Peskov said.

Biden reiterated on Wednesday the United States' commitment to countering Russian aggression on Ukrainian land.

"Today's announcement builds on the hard work and commitment from countries around the world led by the United States of America to help Ukraine defend its sovereignty and its territorial integrity. That's what this is about: helping Ukraine to defend and protect Ukrainian land. It is not an offensive threat to Russia," he said.

More international commitments coming, official says

"We do expect 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," an official told reporters earlier Wednesday.

Ukraine wants American and German tanks quickly, as they're more advanced than Russia's own.

"Hundreds of thanks are not hundreds of tanks," Zelenskyy said last week. "All of us can use thousands of words in discussions, but I cannot put words instead of the guns that are needed against Russian artillery or instead of the anti-aircraft missiles that are needed to protect people from Russian air strikes."

The Biden administration last week had announced another huge military aid package for Ukraine -- including close to 150 more armored vehicles -- but not the Ukraine-requested tanks.

ABC News' Libby Cathey, Shannon K. Crawford, Luis Martinez, Matt Seyler and Joseph Simonetti contributed to this report.