Due to poor morale and fuel and food shortages, some Russian troops in Ukraine have surrendered en masse or sabotaged their own vehicles to avoid fighting.

A senior Pentagon official refers to such a statement in an article published on Tuesday by the New York Times. Some entire Russian units laid down their arms without a fight after facing surprisingly tough Ukrainian defenses, the official said. Some Russian invaders deliberately poked holes in the gas tanks of their vehicles, presumably to avoid combat.

However, a Pentagon spokesman declined to say how the military made these estimates - presumably from a mosaic of intelligence data, including statements by captured Russian soldiers and intercepted communications.

In addition to addressing fuel, food and spare parts shortages, the Russian commanders leading this armored column towards Kyiv may also be "regrouping and rethinking" their battle plans, making adjustments on the fly to gain momentum, according to a Pentagon spokesman, for "an inevitable push in the next few days to encircle and eventually capture the capital."

The officials said more than 80% of 150,000 the Russian invasion forces has already been deployed.

U.S. said analysts were struck by the "risk-averse behavior" of such a large force.

Russia landed an amphibious assault to capture Mariupol, a key port city on the Sea of ​​Azov, but landed about 40 miles from the city. They added that the vaunted Russian air force has yet to gain air superiority over Ukraine as Russian warplanes are countered by Ukrainian fighter jets and a surprisingly resilient and powerful air defense system.