BRUSSELS, Jan 9 (Reuters) - Belgium has reached an agreement with French utility Engie to extend the life of two Belgian nuclear reactors by 10 years, the prime minister said on Monday.

"The extension of these two nuclear reactors is crucial to guarantee our energy security," Belgian Prime Minister Alexander De Croo told a news conference after a meeting of key cabinet members.

He added that not all details of the agreement had been finalised. (Reporting by Charlotte Van Campenhout, editing by Geert De Clercq and Philip Blenkinsop)