The secretary general of NATO will call for a 400% increase in funding for air and missile defences, during a speech in London today.
Mark Rutte will be meeting with the prime minister and John Healey, the defence secretary, this afternoon.
It comes ahead of a summit in The Hague later this month, when the UK and its NATO allies are expected to agree to pledge to spend 5% of GDP on defence and related areas.
Currently, the government is committed to spend 2.5% GDP on defence from April 2027, with a goal of increasing this to 3% over the next parliament.
Sky News understands that the government will in fact increase defence spending to 3.5% of GDP within a decade to keep the US on side.
'Hope is not a strategy'
Speaking at Chatham House, Rutte will call for a "quantum leap in our collective defence".
He will say that "danger will not disappear even when the war in Ukraine ends".
The call for a 400% increase in air and missile defence will come because of how Russia "delivers terror from above".
Rutte will say that NATO countries must "strengthen the shield that protects our skies".
As well as this, he will call for these countries to produce thousands more armoured vehicles, tanks, shells, and improve logistics, supply and medical support.
Rutte will warn: "Wishful thinking will not keep us safe. We cannot dream away the danger. Hope is not a strategy.
"So NATO has to become a stronger, fairer and more lethal alliance."