Russia's war in Ukraine

US-owned M1A2 Abrams tanks in Germany. (Daniel Karmann/picture alliance/Getty Images)

The US will send the M1A2 Abrams tank to Ukraine, which has significantly upgraded capabilities compared to the earlier M1A1 model.

Deputy Pentagon press secretary Sabrina Singh confirmed Thursday that the M1A2 would be the version of the Abrams provided to the Ukrainians. She said that the US does not “have these tanks available in excess in our US stocks,” and it will take “months to transfer” the tanks to Ukraine.

The M1A2 is a significant upgrade from the older M1A1, mostly due to the fact that the A2 runs on a digital system, as opposed to the analog system of the A1.

It’s “the difference between a plug-in phone – a rotary phone – and that iPhone you’ve got in your hand,” explained retired Army Gen. Robert Abrams, the former commander of US Forces Korea, whose father was the namesake for the 70-ton tank.

US officials announced this week that 31 Abrams tanks would be sent to Ukraine after days of back and forth between the US and its allies. Officials had not yet disclosed which tank variant they would choose, and Army acquisitions chief Doug Bush told reporters on Tuesday that the decision was still being deliberated.

More on the tanks: US President Joe Biden said from the White House on Wednesday that the tanks would “enhance Ukraine’s capacity to defend its territory and achieve its strategic objectives.”

In addition to the digital change with the A2, the newer version of the tank is “significantly” more lethal than the A1, Abrams said. It includes a commander’s independent thermal viewer. Whereas before, only the gunner had a thermal site, now the tank commander has one as well, allowing them to help scan for and identify targets. The digital system also allows the tank crew to run their own onboard diagnostics, Abrams said, instead of waiting for mechanics to run tests to determine any issues that arise.

When it comes down to it, Abrams said, the M1A2 is “far superior in lethality and survivability and mobility” to anything that Russia has on the battlefield.

It’s unclear which variant of the A2 tank, of which there are three, will be chosen. Singh declined to say during the Pentagon briefing Thursday, and Bush declined to say Wednesday.

Bush added that concerns over logistics and maintenance for each variant – which had frequently been cited as a reason the US was hesitant to send the Abrams at all – would not weigh heavily on the decision.

He also explained that the Army does not produce brand new tanks from scratch and has instead been modifying existing older models. “That doesn’t mean it’s easy or fast necessarily,” he added, but they don’t currently have to be built from scratch.

CNN’s Michael Conte contributed reporting to this post.