Sanctions imposed against Russia by the West will not stop President Vladimir Putin's moves against Ukraine, according to a Russian studies expert from Harvard University.

Dr Alexandra Vacroux, of Harvard’s Davis Center for Russian and Eurasian Studies, told Prime Time that she was pessimistic about the sanctions announced in the wake of Mr Putin’s decision to order troops into two regions in the east of Ukraine.

"The sanctions are not going to stop the Russians. One of the things that Putin said in his speech yesterday is that 'you're going to sanction us no matter what.’ So it makes no difference what we do," Dr Vacroux said.

"They are not really a deterrent anymore – they are punishment and, because they are punishment, we still have to impose them. But they are not going to change Russian behaviour in terms of the impact on Russia."

However, Dr Vacroux said that excluding Russia from the Swift messaging system, which is used by banks to transfer money to other financial institutions, is one potential sanction that could have an impact.

"If Russia is kicked out of that, the way Iran was, that could be a very severe blow to their economy," said.

Dr Vacroux said that Russia was unlikely to impost retaliatory sanctions on the West. But she pointed to Europe's dependence on Russian gas.

"Russia's big leverage is the fact that they are supplying so much oil and gas to Europe. It's cold, and now is an excellent time to reduce gas supplies," she said.

"The other thing they could do is a cyberattack on some of the infrastructure, both in Europe and in the United States," Dr Vacroux said.

"We know from the SolarWinds attack last year, and also the shutdown of the colonial pipeline, is that they have already put in a lot of malware into our infrastructure systems in the West. And it's just a question of them activating it in order to disable some of our key infrastructure."

Dr Vacroux told Prime Time that it was "inevitable" that a minor war over Ukraine would occur, saying that we were "likely to see Ukrainian and Russian troops fighting each other in the coming days."

"The big question is whether this war could spread beyond just Russian and Ukrainian troops. To some extent, that depends on whether NATO is so concerned about what the Russia plans to do," she said.

"For example, if they plan absorb Ukraine completely that they would then decide that NATO troops need to go into Ukraine, into the theatre and fight the Russians."