British Foreign Secretary Liz Truss accused Russia on Saturday of not being “serious about diplomacy” while warning that the “worst-case scenario could happen as early as next week.”

Truss also said Ukrainian President Volodymyr Zelensky's speech at the conference was “extremely sobering.”

Truss said the United Kingdom would stand in unity with its partners to support Ukraine.

“We need to be strong because that is the only thing that Russia understands. And I think we need to be strong in supporting Ukraine and not selling Ukraine out with concessions on sovereignty,” Truss said.

“Ukraine needs our support at the United Nations and at the OSCE and they also need our economic support because there is a real threat of economic destabilization. They need our defense support, and the UK is committed to continuing to supply that support, standing shoulder to shoulder with Ukraine,” she added.

The foreign secretary stressed that the UK is “resolute in imposing severe costs on Russia in the event of an invasion, including tough sanctions.”

“We will stop oligarchs being able to move their money internationally. We will stop them traveling, and we will make it tougher for Russian companies to tap into our capital markets. And we're also going to make it harder for Russia to access sovereign debt markets,” she said.

Truss said the UK stands with Europe and the United States in being “completely united in support of Ukrainian sovereignty and self-determination.”

“What this crisis has demonstrated is we are united. We are prepared to put tough sanctions in place in the event of an incursion. We are prepared to supply that defensive support to Ukraine,” Truss said.