LONDON, (Reuters) – Boris Johnson, the British Prime Minister will speak to the nation Thursday. He’ll then set out “the most severe” sanctions against Russia following its invasion of Ukraine.

In his earlier tweets (NYSE:), British leaders called the invasion “catastrophe” in Europe and promised to talk with other G7 members.

After earlier this week’s imposition of a restricted initial package, which was criticised as weak in response to Russia’s recognition that two regions were separate from Ukraine, Western countries are likely to announce coordinated sanctions Thursday.

Johnson tweeted, “This is a disaster for our continent.” “I will give an address this morning to the nation on the Russian invasion Ukraine.”

“I’ll also be speaking to other G7 leaders, and I call for an urgent meeting with all NATO leaders as quickly as possible.”

Liz Truss, Foreign Minister of Ukraine said she called the Russian Ambassador to discuss Moscow’s conduct in Ukraine.

Britain had, just like the United States, threatened tougher sanctions to Russia in case it invaded Ukraine. Russian President Vladimir Putin earlier stated that Moscow would not do this.

Johnson said Wednesday that he was ready to impose sanctions against Russia in the next “toughest” tranche. Johnson described this as a way to make a change and alter the outcome.