The UK has committed to a "significant upgrade" of its fleet of Type 45 destroyers.
In doing so, the UK is set to become the first European nation to operate a Maritime Ballistic Missile Defence capability that can detect and destroy Anti-Ship Ballistic Missiles.
The upgraded defence system will help UK forces combat the increasing threats posed by anti-ship ballistic missiles at sea by developing the missile into a maritime variant.
The Ministry of Defence (MOD) has placed an initial contract for this work with Missile manufacturer MBDA which, when delivered, will be worth more than £300m and support more than 100 jobs across the UK.
Defence Procurement Minister Jeremy Quin said: "As we face global uncertainty, alliances and greater defensive capability are more important than ever.
"Joining our French and Italian counterparts will see us collectively improve the cutting-edge technology our Armed Forces possess."
The signing of the tri-national agreement is the first formal step in the upgrade of the six Type 45 vessels.
This will include converting existing missiles to the ASTER 30 Block 1 standard, previously used only in French and Italian land systems, as well as updates to the SAMPSON multi-function radar (MFR) and Sea Viper command and control missile system, under the full Sea Viper Evolution programme.
Sea Viper's upgrade will boost the lethality of the Type 45 vessels, hoping to ensure the Royal Navy remains poised to defend the surface fleet and the Maritime Strike Group against complex air threats.
The Sea Viper Evolution programme follows recent contract awards to introduce the Common Anti Air Modular Missile (CAMM) into the Type 45.
This will see the missile outload of the platform increase from 48 to 72 missiles.
The Royal Navy's Type 45 destroyers are among the most advanced in the fleet and carry out a range of roles, including defence from air attacks, counter-piracy operations and providing humanitarian aid.
There are six in the fleet – HMS Dragon, HMS Defender, HMS Diamond, HMS Duncan, HMS Dauntless and HMS Daring.
Defence Command Paper
Upgrading the defensive capability of the Type 45 fleet was committed to in the Defence Command Paper, as part of the Integrated Review last year.
Being able to defend against anti-ship ballistic missiles will add to the current capability of the destroyers to defeat threats from the air.
Mr Quinn added: "It is another example of us delivering on the commitments from the Defence Command Paper, helping protect our service personnel when faced with the most severe threats."