France, the world's most nuclear energy-dependent nation, is taking its first steps to shift to more renewables to power up.

On Saturday, the country begins a gradual shutdown of its aging Fessenheim plant. The move fits into the government's broader energy strategy to reduce French dependence on nuclear energy from supplying three-quarters of its electricity to about half by 2035.

Prime Minister Edouard Philippe says the plant's first reactor will be closed Saturday, and the second in June.

Another dozen reactors must close by 2035 to meet the phase-down target. The plan also sees France closing its remaining coal plants, and moving to renewables like solar and wind to close the energy gap and help fight climate change.

For Charlotte Mijeon, spokesperson for anti-nuclear group Sortir du nucleaire, the Fessenheim shutdown is welcome news - but not enough.

"It's great that it's eventually closed; however, we fear that Fessenheim is something like the tree hiding the forest," she said. "The government is closing one nuclear power plant, but it should not make us forget that the rest of the nuclear fleet is aging."

France has 58 nuclear power plants, thanks to an energy strategy dating back to the 1970s oil crisis. Supporters say nuclear energy is a clean way to fight climate change while also meeting national energy needs.

But critics say the plants have received billions in subsidies and nuclear lobbies are powerful, making it harder for renewables to compete. And they say the remaining plants pose mounting safety concerns as they age.

"Regarding the climate emergency, we have no time left," Mijeon said. "So we have to invest in green climate solutions, not in nuclear power, which is not only dirty, but also very expensive and slow."

While the reactor shutdown is a first for France, other countries, including Switzerland, Sweden and the United States, have also shut plants for a mix of budgetary, safety and environmental reasons.

Neighboring Germany aims to phase out of nuclear power completely by 2022. It has been pushing for years for the shutdown of Fessenheim, which is located near its border.