On Sunday, rockets reportedly destroyed an air defence installation in the Russian city of Belgorod equipped with S-300/400 surface-to-air missiles.

The Kremlin later warned Washington it could suffer “fatal consequences” for backing the cross-border attacks.

“A last we will be able to move them back a bit,” one infantry soldier told The Telegraph.

“Maybe it will give us some breathing space. It’s been very frustrating.”

Another said: “Yes, we have to be able to strike them. We didn’t invade them, they invaded us.”

Troops described difficult conditions at the front. They said while ammunition had started to reach their lines after a lengthy political hold-up to US supplies, Ukraine’s forces were still heavily outgunned.

‘We need to kill Russians’

“If we use 10 shells, they send 50 back,” said one artillery gunner.

“Even if we receive the shells, our artillery barrels are old and worn out.”

Allowing strikes inside Russia would help he predicted, though he said cross-border strikes would probably be a tiny proportion of Ukraine’s overall targeting.

He said: “Of course, they should give us this option. We will not use it against civilians, we will use it against military targets.

“We need to kill Russians so they don’t come here.”

Vovchansk has been largely destroyed since the start of the May 10 offensive.

Up to 80 per cent of the town’s buildings are reported to have been damaged.

Troops said the front line had stabilised in recent days and Ukrainian commanders have estimated they still control 70 per cent of the town.

Troops still face the threat of Russian artillery superiority and glide bombs which can be launched by Russian jets from well beyond the range of Ukraine’s air defences.

Mykhail said ammunition shortages had eased with the unblocking of US supplies.

He said: “Of course, it was very painful at the end of 2023. Now we can use artillery. It’s not possible to fight just using infantry.

“If our allies also continue supplying more, then we can save more Ukrainian lives.”

The cost of more than two years of Russia’s invasion is clear at Kharkiv’s No 18 cemetery. One section contains around 1,200 new graves covered by a sea of national and military flags.