The U.S. plans to send Ukraine a more advanced configuration of Abrams tanks, the M1A2, rather than the older A1 version. But the 31 tanks destined for Ukraine will not include the secret armor alloy that makes the newest army version of the tank deadly, Politico reported, citing sources.

The A2 version has more sophisticated optics and controls than the older A1 version, which the Army intends to retire in the next few years. Externally similar to the A1, the A2 has a redesigned combat module with improved optics for guidance and an independent thermal imager that allows the commander to scan targets independently in all weather and combat conditions.

The most radical changes are to the interior, which has been redesigned to incorporate new technology. Using the new technology, commanders can quickly track the location of friendly vehicles, determine enemy positions and handle artillery requests.

But federal policy prohibits exporting Abrams with classified armor kits used by the U.S. military that include depleted uranium. The U.S. strips the tanks of this secret prescription armor before selling them to other countries. There are other armor kits that the U.S. can provide to foreign military buyers.