French President Emmanuel Macron is set to throw his support behind a massive nuclear power plant program on Thursday despite concerns about the cost and complexity of building new reactors.

The head of state will go to a key turbine manufacturing site in eastern France on a pre-election visit dedicated to energy policy and the future of the country's atomic industry, which provides around 70 percent of French electricity.

Low-cost nuclear power has been a mainstay of the French economy since the 1970s, but recent attempts to build new-generation reactors to replace older models have become mired in cost over-runs and delays.

Macron is set to announce the construction of at least six new reactors by state-controlled energy giant EDF by 2050, with an option for another eight, a source close to the president told AFP on condition of anonymity.  

"It (nuclear) is ecological, it enables us to produce carbon-free electricity, it helps give us energy independence, and it produces electricity that is very competitive," another presidential aide told reporters on Wednesday.

Whatever the 44-year-old head of state announces will depend on the outcome of presidential elections in April, however, with his rivals likely to review and change his proposals if they defeat him.

Most presidential candidates have vowed to continue investing in the industry with the exception of hard-left candidate Jean-Luc Melenchon and Greens contender Yannick Jadot who object to it on environmental grounds.

French-German split

The French government lobbied hard -- and successfully -- to have nuclear power labelled as "green" by the European Commission this month in a landmark energy review which means it can attract funding as a climate-friendly power source. 

Macron has consistently argued that nuclear energy is required to help advanced economies transition to a low-carbon future, with ministers frequently citing German policy as an example of what can happen if it is abandoned.

Germany decided to phase out nuclear industry by the end of 2022 following the 2011 Fukushima nuclear disaster, but the decision has been criticised for increasing Berlin's reliance on carbon-emitting gas and raising power prices.

The new French programmes comes as heavily indebted EDF faces difficulties in trying to build its latest-generation EPR reactors in separate projects in France, Britain and Finland. 

Its flagship French project, in Flamanville in northern France, is expected to cost around four times the initial budget of 3.3 billion euros ($3.8 billion) and will not be loaded with fuel until next year at the earliest -- 11 years later than expected.

The Flamanville overruns have been denounced as "a fiasco at the French public's expense" by Jadot.

Turbines

Macron is set to law out his vision "of our future energy mix, for nuclear but also renewables and energy efficiencies," according to the aide.  

He will speak in Belfort, home to a key manufacturing site that produces turbines that will be used in the future power stations.

The site was sold by French industrial giant Alstom to American rival General Electric in 2015 in a widely criticised deal associated with Macron who was economy minister in the Socialist government at the time.

The divestment led to more than a thousand job cuts and fears about the loss of a strategic industry to a foreign investor.

Under pressure from the French government, EDF announced Thursday that it had agreed a deal to buy back the unit at a cost of 200 million dollars (175 million euros).