WARSAW (Reuters) - Polish and Lithuanian power grid operators said on Friday they had agreed to build a high voltage direct current (HVDC) underwater cable by 2025 as part of a plan to connect the electricity grids of the Baltic states with those of the European Union.

Poland’s PSE and Lithuania’s Litgrid said they signed an initial cooperation agreement regarding what they called a “Harmony Link”, with an investment decision expected in 2020.

EU Climate Commissioner Arias Canete was quoted in a statement as saying the cross-border project was a clear sign of how political and professional accords were helping the three Baltic states gain full control of their electricity networks.

In June, the leaders of the Baltic states and Poland signed a long-awaited deal to connect their power grids to the European Union by 2025 and break their dependence on Russia, a Soviet legacy.

Under the deal, states would use the existing overland LitPol Link between Lithuania and Poland, as well as the planned cable under the Baltic Sea, looping around the territorial waters of Russia’s Kaliningrad exclave.