The future of Germany's 17 nuclear power plants, due to be shut down by the early 2020s, is one of the major issues that separates Chancellor Angela Merkel's center-right Christian Democrats from the center-left Social Democrats.

The CDU, along with the liberal Free Democrats (FDP), would like to extend that deadline, a move that is opposed by the SPD and environmentalist Greens.

The issue has been largely ignored in pre-election campaigning for the Sept. 27 general election. But that may now change with Saturday's rally in Berlin, led by farmers from Wendland, a region in north-central Germany, where plans call for permanent waste disposal sites.

The SPD chancellor candidate, Frank-Walter Steinmeier, on Friday accused the CDU and FDP "of leading the country into an energy policy dead-end and endangering domestic security."

But Merkel has said it's too early to turn off the switch on all nuclear power in Germany.

"We cannot phase out nuclear energy as quickly as some imagine," Merkel said. "But in the long term, that's to say in the second half of the century, we will experience a large amount of renewable energy sources. We are convinced that we will be able to stop using nuclear energy at some point."

A divisive issue and maybe a rallying cry

Tractors heading to Berlin for Saturday's rally

Political analysts have said that even though the dispute between the CDU and SPD has had little effect on the campaign, the nuclear issue could mobilize voters in both camps.

"So far, it has played almost no role at all, which is a bit surprising, considering it's one of the few issues where the CDU and SPD are completely at odds," said Dietmar Herz, a political scientist at Erfurt University.

The SPD and Greens point to polls showing that a majority of Germans - around 59 percent - oppose nuclear energy and want the plants shut down, while the CDU and FDP emphasize that until Germany has built up a significant infrastructure of alternative energies, nuclear power plants should remain on line.

In 2001, the SPD-Green government under former Chancellor Gerhard Schroeder pushed through legislation to phase out the use of nuclear energy within two decades, despite protests from the industry and power utilities.

Germany at odds with most other developed countries

Nuclear waste is transported under heavy guard in special containers

The SPD and the Greens had hoped that Germany would lead the way into a "post-nuclear age," but instead much of the developed world has embraced the use of nuclear power as part of a climate-friendly energy mix. France, for example, gets 80 percent of its power from nuclear energy and even exports a significant amount of it to Germany.

Germany covers about 23 percent of its energy consumption with nuclear power, compared to 42 percent with coal-fired power stations, 14 percent with natural gas and 15 percent with renewable energy sources, such as wind, solar and thermal.

Nils Diedrich, a political scientist at Berlin's Free University, said he expects discussions about nuclear issue to heat up if Merkel is able to form a coalition with the Free Democrats after the September election.

"If the CDU and FDP do actually win power and push through an extension of nuclear power we'll see a real battle," he said. "Then there will be massive demonstrations."

gb/dpa/Reuters/afp

Editor: Nick Amies