Russian paramilitary group Wagner's chief Yevgeny Prigozhin said on Thursday that the group eyes to capture the Bakhmut area in Ukraine in March or April.
In messages distributed online overnight, he said progress would depend on whether "the adversary sends reserves" and blasted Russia's "monstrous military bureaucracy" for its failure to seize the Donetsk region city before the end of 2022.
The fierce fighting for the eastern industrial city is the longest running battle of Russia's near year-long intervention.
"I think it's (going to be in) March or in April," Wagner head Yevgeny Prigozhin said in one of several messages posted online overnight.
"To take Bakhmut you have to cut all supply routes. It's a significant task," he said.
The 61-year-old, who is close to President Vladimir Putin, said the speed of Russian progress in the grinding battle would depend on whether Ukraine continued to send reserves to hold the city.
Prigozhin's private fighting force, which has recruited from prisons across Russia to bolster its ranks, has claimed a lead role in recent battles in east Ukraine.
He announced last week that Wagner would no longer be drawing from prisons to fill its ranks and on Thursday said this would impact their fighting potential.
"Of course, at some point the number of units will drop and as a result the number of tasks that we can perform will not be what we want," he added.
Wagner claims to have captured ground without help from the regular army, spurring friction between Wagner and Russia's trop brass, which Prigozhin criticised for being mired in "monstrous" red tape.
"Progress is not going as fast as we would like," he said in one of the messages posted on the Telegram social media platform.
"I think that Bakhmut would have been taken before the New Year, if not for our monstrous military bureaucracy, let's say, and not for the spokes that are put in the wheels daily," he added.
