LONDON -British Defence Secretary Ben Wallace said on Thursday it would be legitimate for Ukrainian forces to target Russian logistics to cripple their supply of food, fuel and munitions but they were unlikely to use British weapons to do so.
Tensions between Britain and Russia increased this week when Moscow accused London of provoking Ukraine to strike targets inside Russia, saying there would be an immediate "proportional response" if it continued.
Wallace said under international law Ukraine had every right to defend itself.
"Part of defending itself in this type of invasion is obviously where Ukraine will go after the supply lines of the Russian army because without fuel and food and ammunition, the Russian army grinds to a halt and can no longer continue its invasion," he told BBC TV.
Britain has been a vocal supporter of Ukraine since it came under attack in late February, sending aid and arms to help it repel its larger neighbour.
Wallace said Britain had sent artillery to Ukraine that was being used within Ukraine on Russian forces, but he added that it had not, and was unlikely, to send weapons that could be used for longer-range attacks.
He said that it was not clear if attacks seen in Russia in recent weeks had come from the Ukrainian state. He added that Ukraine did not have British weapons that could do that.
Ukrainian forces, he said, tend to use mobile launchers while the British army would deliver them from the air or sea.
"They currently don't have British weapons that could do that, so it's unlikely that it is our weapons," he said. "We're very unlikely to supply that to anyone simply because of the technology and also the scarcity we have of those capabilities. So it is very unlikely."
Wallace also denied that NATO was locked in a proxy war with Russia but said the West would provide increasing support to Ukraine if the Russian attacks continued. "Sometimes that will include planes and tanks," he told Times Radio.
Russia on Wednesday reported a series of blasts in the south of the country and a fire at an ammunition depot.
Russia has repeatedly criticised Britain's military support for Ukraine, accusing it of wanting to prolong the conflict to weaken Moscow.
Responding to a similar British statement on Tuesday which said Russian military targets inside Russia were fair game for Ukraine, Russian Foreign Ministry spokesperson Maria Zakharova suggested that British logic meant Russia was also theoretically entitled to strike targets in NATO countries like Britain if they were related to arms deliveries for Ukraine.