French energy group Engie and the Belgian government signed a deal Thursday extending the life of two nuclear reactors by a decade after Russia's war in Ukraine prompted Brussels to delay its nuclear exit.

Belgium had planned to abandon nuclear power in 2025 but it decided last year to keep it for another 10 years as European nations scrambled to find alternatives to Russia's energy exports.

"This agreement is important for our energy future and for Belgian households," Prime Minister Alexander De Croo said in a statement.

"It strengthens our electricity supply, reduces our country's energy dependence and guarantees the production in Belgium of low-carbon and cheap electricity," he said.

Wedged between nuclear-powered France and gas-and-coal-dependent Germany, Belgium has relied on an ageing stable of seven nuclear reactors operated by Engie for about half of its electricity needs.

The promise of a gradual phase-out of nuclear power has been enshrined in Belgian law since 2003, and the decision to delay the moratorium was fiercely resisted by the Greens party.

The plan outlined last year saw Belgium's fragile coalition government agree to extend the operating lives of the Doel 4 reactor near the port city of Antwerp and Tihange 3 near Liege until 2035.

The deal with Engie was sealed after fraught negotiations over the future costs of nuclear waste management.

The French firm said Thursday the costs were set at 15 billion euros ($16.4 billion) and would cover the waste from Engie's seven nuclear plants in Belgium.

Engie will also have to pay eight billion euros for the future dismantling of the plants.