The German Environment Minister, Sigmar Gabriel, has called for seven of the country's oldest nuclear reactors to be closed down immediately.
The German nuclear industry wants to keep older plants running longer
Justifying his demand, Mr Gabriel pointed to recent breakdowns at two ageing nuclear plants.
Germany is committed to phasing out nuclear power by 2020.
Mr Gabriel told a German newspaper that it would be of great technical benefit from the safety standpoint to close the oldest reactors now.
As a trade-off, newer reactors could be kept running longer.
Mr Gabriel is a member of the Social Democrats, whose previous coalition government with the Greens drafted the nuclear switch-off policy.
Now they are sharing power with the more nuclear-friendly Christian Democrats, they face a battle to maintain the strategy.
But if there is to be any trade-off in capacity, the nuclear industry, including the unions, would rather give up some output from newer plants to keep the older ones going longer.
It is technically feasible: in the United States, some plants have had their design life of 30 years doubled. But it would require a political about-turn.
So far, two of Germany's 19 nuclear plants have been shut down.
European opinion on nuclear power is divided in the face of Russia's growing assertiveness in the gas and oil markets, not to mention the need to meet targets for reducing carbon emissions.
As a result of a referendum after the Chernobyl disaster, Italy shut down the last of its four nuclear plants in 1990, but it is now one of the world's largest net importers of electricity, and the policy is under review.
France, which generates 80% of its electricity from nuclear power, shows no signs of stopping.
Finland in 2002 gave the go-ahead to build a fifth nuclear plant, pioneering the new European Pressurised Reactor - ironically, using Italian technical know-how.