"The €27 billion investment will modernize NATO's existing fuel facilities and the infrastructure for fuel storage and distribution," NATO wrote in a statement on Thursday.
It added that the investment will be used for new facilities and pipelines in Eastern and Southeastern Europe to "ensure that NATO forces have the energy supply required for combat readiness."
The 5,300-mile pipeline network in central Europe was built in the late 1950s to supply alliance forces with fuel during the Cold War.
Upgrading the system will take about 25 years.
