The UK is also buying three new SEAL Delivery Vehicles, submersibles used to transport special forces from submarine to their target.
For the UK, the special forces are members of the Royal Navy Special Boat Service (SBS).
In the latest announcement of proposed foreign military sale (FMS) deals, the US Defense Security Cooperation Agency said the UK wanted to buy 50 Phalanx Close-in Weapon System (CIWS) Block IB Baseline 2 Upgrade Kits, along with support equipment, test equipment, initial spare parts, technical documentation, training, and engineering technical assistance.
The total estimated cost is US$75 million.
DSCA said this proposed sale would support US foreign policy and national security objectives by improving the security of a NATO ally “which has been, and continues to be, an important partner on critical foreign policy and defence issues”.
“The UK, which already has earlier versions of the MK 15 Phalanx in its inventory, will have no difficulty absorbing these upgrades and support into its armed forces,” DSCA said.
The prime contractor will be defence company Raytheon Missile Systems.
DSCA said the UK had also requested to buy three SEAL Delivery Vehicles MK 11 Shallow Water Combat Submersibles, along with spare parts, handling and test equipment, documentation, and technical and logistic support.
The total estimated program cost is US$90 million. The prime contractor will be Teledyne Brown Engineering of Alabama.
DSCA said the proposed sale of the SEAL Delivery Vehicles would continue the UK's maritime partnership with the US, enhancing interoperability and regional security capability.
“The UK has a proven track record of successfully deploying predecessor system. The UK will have no difficulty absorbing this system into its armed forces,” it said.
The Mark 11 is the latest version of the Mark 8 SEAL Delivery Vehicle (SDV), used by US Navy SEALs and the UK SBS.
This is a 17-tonne, 6.7-metre-long submersible able to transport a crew of two- and four-member combat swimmer team more than 30 kilometres at a cruising speed around 7 km/h.
Propulsion is an electric motor powered by lithium-ion batteries and maximum depth is around six metres.