據美國新聞媒體報導這是由於烏克蘭的抵抗強於預期。

Russian offensive unexpectedly slowed by fierce Ukrainian resistance
https://www.nbcnews.com/news/world/...tance-rcna17703

Russia-Ukraine live updates: Russians frustrated by lack of momentum: US official
https://www.yahoo.com/gma/russia-uk...-195800395.html