Hitachi Ltd. is set to buy Finmeccanica SpA's rail business and a signals affiliate in its largest ever overseas acquisition as it seeks growth abroad.

The Japanese industrial group, which makes nuclear power plant turbines, electronic equipment and industrial machinery will close the acquisitions of AnsaldoBreda SpA and Ansaldo STS SpA later this year, the companies said in a joint statement. Finmeccanica said in November it had received an offer from the Japanese group.

Hitachi has sought to expand overseas as Japan's population declines and most nuclear power plants in the country remain shut after the 2011 earthquake and tsunami led to a triple meltdown at Tepco's Fukushima No. 1 nuclear power plant. Finmeccanica Chief Executive Officer Mauro Moretti is selling the rail unit to focus on faster-growing helicopter, aerospace and defense-electronics businesses and cutting debt at the company owned 32 percent by the state.