There is a "realistic possibility" Russia has diverted troop resources around Donetsk city toward Bakhmut, the U.K. Defense Ministry wrote in its April 18 intelligence update.
Russian forces are continuing to make "creeping advances" in Bakhmut, according to the ministry.
Ukraine is holding Russian forces back in the south of Bakhmut by maintaining control along Korsunskovo Street, the main road leading west out of the town.
The ministry also noted that the specific order and timing of any major withdrawal of Ukrainian and Russian military units is becoming an important logistical issue.
Ukraine likely aims to redirect some of its military units deployed in Bakhmut for the planned counteroffensive, while Russia seeks to rebuild its operational reserves before redeploying them.
The battle of Bakhmut has been raging for the past nine months with the Russian military attempting to increase its grip over the entirety of the oblast, around half of which it currently occupies. Both sides have sustained heavy casualties.
As of mid-April, Ukrainian forces continue to hold parts of the city, west of the railway line, while Russian forces led by the Wagner Group have taken the administrative center.