Russia will be “punished” if the country pushes ahead with any “destabilising action” in Ukraine, Downing Street has warned.

US Secretary of State Antony Blinken is holding last-ditch talks with Russian diplomats in Switzerland on Friday in a bid to avert a conflict on Ukraine’s border, where Moscow has amassed an estimated 100,000 troops.

Number 10 said if Russian President Vladimir Putin launches an offensive, there will be a “package of sweeping measures” launched by the UK and its allies against the Kremlin.

Earlier, Foreign Secretary Liz Truss warned Mr Putin he must “desist and step back” from war in Ukraine or risk being dragged into a prolonged conflict like the Soviet invasion of Afghanistan.

Speaking at the Lowy Institute in Sydney, she said: “If there is an incursion by Russia into Ukraine, it would come at a massive cost.

“We are prepared to put very severe sanctions in place, we are also working to support Ukraine in terms of defensive capability.”

A spokesman for Boris Johnson said: “I think the Prime Minister has been clear that any destabilising action by Russia in Ukraine would be a strategic mistake and would have significant consequences.

“I’ve talked about the fact that we’re working closely with our partners, including the US, to draw up a package of sweeping measures to make sure that the Russian government is punished if it crosses the line.”

Earlier, former British ambassador to the US Lord Kim Darroch said Mr Putin wants to “recreate the Soviet Union”.

Liz Truss
Liz Truss is currently in Sydney for talks with Australian leaders (Rick Rycroft/AP)

Lord Darroch said Mr Putin does not like the direction of the Ukrainian government.

“He is trying to bully them and intimidate them,” he told BBC Radio 4’s Today programme.

Ms Truss said as well as dealing with the immediate threat, the “free world” also needs to dial down its “economic dependence” on Russia.

She said this will mean that “in the future it becomes harder for those aggressive regimes to use economic dependence as a way of getting what they want”.

She added: “We are very ready to act in the immediate term.

“In the longer term, this is why it’s so important that we are investing in developing countries – it’s so important that we are trading widely across the world using strong rules-based agreements like the CPTPP (Comprehensive and Progressive Agreement for Trans-Pacific Partnership).

“That’s the West’s way to protect ourselves from aggressors – from a position of economic and defensive strength.”