Milley and Austin have cited how long it takes to train personnel to operate the tanks and how difficult the tanks are to maintain. They also have argued they are not the right vehicles for the fight in Ukraine right now, according to the officials.

One U.S. official said Austin has argued the training to operate and maintain the tanks would take months, and even though the Ukrainians have proven adept at learning many new platforms, he continues to resist sending the Abrams. 

Two U.S. officials also noted that Ukraine already has hundreds of tanks at its disposal and over the past year has captured hundreds of Russian tanks on the battlefield and added those to its inventory.

NBC Why top U.S. officials don’t want to give Ukraine tanks