Ms Truss also suggested that Germany should “step up” its military support to Ukraine after the UK provided defensive weapons and helped train 20,000 troops in the country.
Asked about German government’s decision to refuse the sale of weapons to Ukraine, the foreign secretary said: “We do need all of our allies to step up,” before adding: “We’re pushing our allies to make sure they are offering similar defensive support.”
It comes as the US put 8,500 troops on alert to be ready to deploy to Europe in case of any escalation, and Western allies agreed to impose “unprecedented” sanctions against Moscow if it were to invade.
Ms Truss said the UK had been working with allies on a package on a “very severe package of sanctions” – but did not reveal whether they were ready to cut Russia off from the global financial payments system SWIFT.
Speaking in the Commons on Tuesday, Ms Truss told MPs she would visit Ukraine next week – saying the UK was “absolutely at the forefront of putting pressure on Russia and supporting our friends in Ukraine”.
She said any Russian military incursion would be a “massive strategic mistake” with “severe cost”. The foreign secretary added: “The Ukrainians will fight – and Putin should beware of an intractable quagmire.”
Labour MP David Lammy said sanctions should be aimed at “cutting Russia out of the global financial system” and urged the government to start “clamping down on the oligarchs who hide their ill-gotten wealth in this capital city [London]”.
Ms Truss said she there would be “severe” economic consequences if Russia invaded Ukraine. “It’s important at this moment that we see all of our partners around the world step up – we are leading by example but we want to see others follow that example.”
Asked if British troops could have a combat role in Ukraine in the event of an invasion, Ms Truss said it was “unlikely that that would be the circumstances … what we are doing is working very hard to make sure Ukraine has the defensive weapons it needs”.
Nato said on Monday it was putting forces on standby and reinforcing eastern Europe with more ships and fighter jets. Russia denounced the moves as Western “hysteria”.
The Kremlin said it was watching with great concern after the US put 8,500 troops on alert to be ready to deploy to Europe in case of any escalation.
The “bulk of” the thousands of US troops placed on heightened alert are planned to bolster the 40,000 multinational Nato troops already in a number of eastern European countries near the border with Russia, according to the Pentagon.
Some Russian-military linked figures have already moved across the border in Ukraine, according to British defence minister James Heappey.
“We are becoming aware of a significant number of individuals that are assessed to be associated with Russian military advance force operations and currently located in Ukraine,” the Armed Forces minister wrote on Tuesday.