British defence minister Ben Wallace said on Monday that he does not expect Russian President Vladimir Putin to use nuclear weapons in his pursuit of Ukraine, days after the former Soviet republic invaded its neighbour.
"We should be worried that a state like Russia believes that the rules don't apply to them, whether that is invading Ukraine or using a nerve agent in Salisbury, but fundamentally a deterrent is what it is, a deterrent," Wallace told Times Radio.
"As much as he might be ambitious for Ukraine, I don't think he wants to go into that space."
Wallace said that Putin had behaved irrationally in deciding to invade Ukraine, and he wasn't going to get into speculation about what Putin would do next, adding that the West would maintain a state of readiness.
But he added that, while Putin had ordered deterrence forces - which wield nuclear weapons - onto high alert, Britain believed that the command served largely a rhetorical purpose and that Putin did not want to use them.
"The language that President Putin has used doesn't actually link to anything of a Russia readiness procedure. It's really, we assess, him putting the deterrent into the communication space, reminding people that he has a deterrent," Wallace said.
"It doesn't link to anything specific in the readiness structures of their forces."
Putin put Russia's nuclear deterrent on high alert on Sunday in the face of a barrage of Western reprisals for his war on Ukraine, which said it had repelled Russian ground forces attacking its biggest cities.
The United States said Putin was escalating the war with "dangerous rhetoric", amid signs that the biggest assault on a European state since World War Two was not producing rapid victories, but instead generating a far-reaching and concerted Western response.
Less than four days after it started, the invasion has triggered a Western political, strategic, economic and corporate response unprecedented in its extent and coordination.
"With this war on Ukraine, the world will never be the same again," EU's foreign policy chief Josef Borrell wrote in an opinion piece in the Guardian newspaper.
"It is now, more than ever, the time for societies and alliances to come together to build our future on trust, justice and freedom. It is the moment to stand up and speak out. Might does not make right. Never did. Never will," he said.
The 27-nation European Union on Sunday decided for the first time in its history to supply weapons to a country at war.
A source told Reuters it would send 450 million euros ($507 million) of weaponry to Ukraine. Borrell at a news conference said EU's support would include providing fighter jets.