"As soon as we have long-range artillery to be able to conduct duels with Russian artillery, our special forces can clean up the city in two to three days," Lugansk regional governor Sergiy Gaiday said in an interview distributed on his official social media channels.
Moscow's forces are concentrating their firepower on the strategically important industrial hub as part of efforts to capture a swathe of eastern Ukraine.
Ukrainian President Volodymyr Zelensky late on Wednesday described the battle as "one of the most difficult" since the start of the war.
Gaiday said on Thursday that Ukrainian forces in the city remained "highly motivated" and "everyone is holding their positions".
"Russia is constantly shelling areas controlled by Ukrainians with artillery," he added.
The Ukrainian presidency said that two strikes overnight had targeted the city's Azot chemical plant and that two sections of the facility were damaged, including an ammonia production centre.
No-one was injured in the strikes, it said, and there was no threat from chemical leaks because potentially harmful substances had been removed earlier.
Some 800 civilians have taken refuge in the Azot chemical factory, according to the lawyer for a Ukrainian tycoon whose company owns the facility.
The United States and Britain have announced they are providing Kyiv with long-range precision artillery batteries, defying warnings from Russian leader Vladimir Putin.
The Ukrainian military announced on Thursday that artillery of Polish origin was ready to be dispatched to the frontline.
The Lugansk region more broadly was under continued mortar, artillery and rocket attacks, the Ukrainian presidency said.
It said four people had been killed and five more wounded in a Russian air strike on Toshkivka, a village around 25 kilometres south of Severodonetsk.
