A “First World War-like” conflict will likely continue in parts of Ukraine for the rest of the year, western officials said on Tuesday.
Both the Ukrainian and Russian armies have suffered “heavy losses” in the 12 months since Vladimir Putin launched his invasion.
Putin’s army has received a boost by help from the Wagner Group, which has enlisted convicts en masse to fight.
The private military has been responsible for significant tactical successes in recent weeks, including taking control of Bakhmut in Donbas.
But Western officials believe a "grinding conflict" of heavy fighting will carry on throughout the year, with neither side making significant gains.
“Both sides are suffering really heavy casualties, in particular around Bakhmut,” they said said during a briefing on Tuesday afternoon.
“It is a devastating First World War-like operating environment and both sides are suffering from logistic challenges.
“There are serious constraints on both sides. What we see is that there is clarity in the force ratio.
“And even though on paper the Russians have greater mass, what we've seen is that they haven't been able to employ that successfully in the battlefield.”
Kyiv’s forces are bolstered by ”superior western military equipment”.
“There is some poor decision making on the Russian side, and there's some pretty agile thinking happening on the Ukrainian side,” they added.
“When you stack up all of these positives and negatives, you end up in some sort of grinding conflict.
“Which at the moment looks like it continues through 2023 unless something else significant changes. Now, it doesn't mean there won't be exchanges of territory.
“But will the exchange of territory lead to a change in the status of the conflict? And at the moment, we can't see that happening.”
It comes after Downing Street said sending British fighter jets to Ukraine would not be “practical” .
The Prime Minister’s official spokesman said: “The UK’s Typhoon and F-35 fighter jets are extremely sophisticated and take months to learn how to fly.
“Given that we believe that it’s not practical to send those jets into Ukraine.
“Obviously, we will continue to provide and accelerate our military support to Ukraine and listen carefully to their requests.”