BERLIN (Reuters) - Britain's defence intelligence service believes that Russia's momentum in the war in Ukraine will slow in the next few months as its army exhausts its resources, British Prime Minister Boris Johnson told a group of European newspapers.

       In comments released on Wednesday by Germany's Sueddeutsche Zeitung, Johnson said President Vladimir Putin's forces were pushing forward in the eastern Donbas region, wreaking destruction but at a heavy cost in soldiers and weapons.

       "Our defence intelligence service believes, however, that in the next few months, Russia could come to a point at which there is no longer any forward momentum because it has exhausted its resources," Johnson was quoted as saying in the interview.

       "Then we must help the Ukrainians to reverse the dynamic. I will argue for this at the Group of Seven summit (in Germany at the weekend)," he said.

       "In as much as the Ukrainians are in a position to start a counter-offensive, it should be supported. With equipment that they demand from us," he said.

       Asked what a victory for Ukraine, or failure for Putin, would look like, Johnson said:

       "That we at least regain the status quo that was there before Feb. 24 and that its (Russia's) troops are repulsed from

       the areas they invaded".

       The interview was also given to France's Le Monde and Italian and Spanish newspapers.

       (Reporting by Madeline Chambers; Editing by Gareth Jones)