Originally Posted by crockett

The aid was a stall tactic, trying to keep the rebels from being over run. This happened previously, when Ukraine forces were taking a city and Russia helped broker a cease fire for a few days, giving the rebels a chance to resupply & set up better defenses.

The food Convoy is the same thing. Russia trying to help the rebels which Ukraine are beating. If the supply convoy was allowed to move forward, Ukraine would have to agree to a ceasefire, which would once again allow the rebels some breathing room to resupply and set up better defenses.