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The Deputy prime minister said those “applying tactics by the Putin regime must be held to account”.
Speaking on Sky News on Sunday, he said this applied “not just (to) Putin himself, but also anyone taking illegal orders”.
“All of those commanders on the ground right through to the people around Putin in the Kremlin, what they do now, whether they give or whether they follow illegal orders to commit war crimes, they will be held to account for it, and they need to know that,” he said.
Mr Raab dismissed Vladimir Putin’s claim that the sanctions levelled against him and Russia were a declaration of war.
“Just to be clear, sanctions are not an act of war. International law (is) very clear about that," he said.
“Our sanctions are entirely both legally justified but also proportionate to what we’re trying to deal with.”
Dismissing fears that the Russian leader would use nuclear weapons in Ukraine crisis, Mr Raab called Mr Putin’s threats “rhetoric and brinkmanship”, and accused the Russian leader of having “a track record as long as anyone’s arm of misinformation and propaganda”.
The Russian president has alarmed the world by putting his arsenal on high alert.
Meanwhile, Russian media cited an unnamed source on Sunday as saying that Ukraine was close to building a plutonium-based “dirty bomb" nuclear weapon, although the source cited no evidence.
“This is a distraction from what the real issues are at hand, which is that it’s an illegal invasion and it is not going according to plan,” said Mr Raab.
He said that Ukrainian forces had “proved a far tougher prospect than Putin expected”. Economic sanctions had “put the squeeze on Putin” and therefore “what he’s now doing is responding with ever more brutal tactics”.
“I think we ought to be under no doubt that our mission with our allies is to ensure Putin fails in Ukraine, and it’s going to take some time." he said.
“We’re talking about months, if not years, and therefore we will have to show some strategic stamina because this is not going to be over in days.”
Urging international leaders to support Ukraine with “everything from military hardware through to cyber resilience”, Mr Raab ruled out a no-fly zone over Ukraine.
Admiral Sir Tony Radakin, the UK’s Chief of the Defence Staff, said such a measure “would not help”.
He told the BBC’s Sunday Morning programme: “The advice that we as senior military professionals are giving our politicians is to avoid doing things that are tactically ineffective and definitely to avoid doing things that tactically might lead to miscalculation or escalation.
“The no-fly zone would not help.
“Most of the shelling is coming from artillery, most of the destruction is coming from artillery. It’s not coming from Russian aircraft.
“If we were to police a no-fly zone, it means that we probably have to take out Russian defence systems and we would have Nato aircraft in the air alongside Russian aircraft, and then the potential of shooting them down and then that leads to an escalation.”