A Russian invasion of Ukraine would be a “very dangerous moment” for the world and could encourage aggressors such as China and Iran, the foreign secretary has warned.

Liz Truss’ warning came as the UK and the US said an invasion was “imminent” as Moscow amasses more than 130,000 troops on Ukraine’s border.

Ms Truss told Sky News: “If we saw an invasion into Ukraine, there would be severe costs in terms of a long-running conflict, we could see the undermining of security more broadly in Europe and could see other aggressors around the world see it as an opportunity to expand their ambitions too.

“This is a very dangerous moment for the world.

“This is, of course, about Ukraine, which is an important sovereign nation but it’s also about the wider stability of Europe and it’s about wider global security.”

The foreign secretary added that the UK is currently in negotiations with Iran over stopping them acquiring a nuclear weapon and she said China has increased its economic coercion and flights over Taiwan.

“We cannot give a message that aggression gets rewards,” she added.

Ms Truss also warned that Russia would “not stop at Ukraine” if it invaded.

“The big risk, of course, is if there is an invasion into Ukraine that will be hugely damaging for Russia and Ukraine. And it will further undermine the stability of Europe,” she said.

“This, I fear, would not stop at Ukraine. This is an attack on the neighbouring states of Russia and other east European countries in trying to undermine legitimacy of them being part of NATO.”