Ed Arnold, a research fellow for European security at the Royal United Services Institute (RUSI) think tank, said Russia is meeting more resistance from Ukrainian troops than it expected.

He told the Reuters news agency on Monday: “At the current rate of Russian losses, which are not confirmed, but we do have indications that this operation would be unsustainable within about three weeks from the Russian perspective.”

He added: “In which case that they would have to consolidate the gains already made and look to see a way of trying to freeze the conflict on the current lines of advance while they mobilise more forces from Russia.”

“In the south, the Russian advance is continued to be slow but they're seeing a lot more successes in the south, taking Kherson and consolidating and pushing further west, and then also focusing now on Mariupol.

“However, at the moment, the Russian operation is going so badly, especially from logistics point of view that really Russia might just not have the numbers to make another conflict that is cold be hot again."

https://ca.yahoo.com/news/russia-operation-ukraine-unsustainable-war-153037343.html