Britain and Ireland will conduct live exercises to test their readiness for incidents involving subsea cables, the two countries' leaders said in a joint statement setting out enhanced maritime cooperation on Friday.
Citing "a more contested environment" and increased hostile state activity, Prime Minister Keir Starmer and his Irish counterpart Micheal Martin said the exercises would begin in September 2026.
Subsea security has become an increasing concern among European nations following a string of power cable, telecom link and gas pipeline outages in the Baltic Sea region since Russia invaded Ukraine in 2022.
The new agreement would, "enable information sharing and coordinated response mechanisms for addressing major subsea communication cable incidents that may affect our countries," the statement said.
Ireland has applied to join a 2024 agreement on subsea security covering the North Sea region, joining Belgium, the Netherlands, Germany, Norway, Britain and Denmark.
Ireland said last month it planned to boost radar and subsea surveillance capabilities and increase cooperation with NATO members amid growing hybrid threats in the North Atlantic
Ireland, which is neutral and has the European Union's lowest level of defence spending, has been criticised for its lack of capability to monitor and defend territorial waters.
(Reporting by William James and Padraic Halpin)