Lithuania's Energy Ministry says the agreement lays the groundwork for a formal, legally-binding contract to build the plant, which could be completed by 2020.
Last year Hitachi beat out Japanese-owned Westinghouse in a tender for the project, which Lithuania wants in order to replace a Soviet-era nuclear facility it closed in 2009 and reduce its dependency on natural gas supplies from Russia.
Hitachi is likely to take an ownership stake in the plant, though the size has yet to be determined.
