British Prime Minister Boris Johnson said Thursday that the Ukraine crisis is at its most dangerous moment and that it is important to take the right action over the next few days.

“To be honest, I don’t think (Moscow) has made up its mind yet. But that doesn’t mean that something absolutely catastrophic can’t happen very soon. And our intelligence, I’m afraid to say, remains grim,” Johnson said at a news conference with NATO Secretary General Jens Stoltenberg in Brussels.

“I would say that probably comes the most dangerous moment over the next few days, and it’s the biggest security crisis Europe has seen in decades. We have to get it right. And I think a combination of sanctions and military resolve along with diplomacy is what is needed.”

Russia is ready to normalize relations with Britain if London is interested, Russian Foreign Minister Sergei Lavrov said at the start of talks with his British counterpart Liz Truss on Thursday.

Disagreements between Russia and the West have sharply escalated over issues of security in Europe and further NATO expansion. Moscow is demanding that Washington and Brussels rule out the possibility of Ukraine joining the North Atlantic Alliance, calling the option of Kiev’s potential entry into the military bloc a “red line,” but the West has no intention of abandoning NATO’s open-door policy under Russian pressure.

At the same time, the West suspects Russia of intending to invade Ukraine, threatening Moscow with severe sanctions. Russia dismisses these suspicions and says it is moving troops across its territory in response to NATO’s actions near its borders