Belgium agreed to extend the life of two ageing nuclear reactors for another decade under a hard-won deal to preserve jobs and invest in the transition to cleaner energy.

The 40-year-old reactors Doel 1 and Doel 2 in northern Belgium will now stay open until 2025 under a deal agreed late Monday with power utility Electrabel that ended years of battling that threatened the country with power blackouts.

"We are determined to write a new page," Gerard Mestrallet, the head of Engie, Electrabel's French parent company, told a press conference Tuesday following tough negotiations over how much Electrabel would invest and pay in taxes.

The reactors' new lease on life will launch a "dynamic to make Belgium a showroom for energy transition," he added.

Mestrallet said his company plans to invest up to four billion euros ($4.2 billion) in new energy projects, such as wind power in the North Sea.

Belgium's energy minister Marie-Christine Marghem said the deal to extend the lifespan of the reactors will keep the country supplied with electricity following fears of blackouts.

She said it would also help Belgium transition to clean sources of energy and keep 18,000 people employed.

The reactors located around 25 kilometres (15 miles) from Belgium's northern port city of Antwerp are currently shut down but, when running, can produce 866 megawatts of Belgium's total electricity capacity of 13,500 megawatts.

Doel 1 was closed on 15 February in line with a 2003 law calling for Belgium's gradual exit from nuclear power between 2015 and 2025. Doel 2 is closed for maintenance.