Prominent German business figures are warning against what they call a too-quick shutdown of the country's nuclear plants, stepping up pressure on Chancellor Angela Merkel's government as it approaches a hard-fought decision on how much longer to keep them running.

The business executives' appeal Friday said Germany, Europe's biggest economy, cannot shift to renewable energy overnight. It still needs energy from coal-fired and nuclear plants, they said.

"A premature exit would destroy billions in capital — to the detriment of the environment, the economy and the people of our country," said the appeal, to be published in newspapers on Saturday.

But the statement didn't specify what "premature" would mean. Merkel's center-right coalition is to decide this fall on changes to long-standing plans to shut the country's 17 nuclear electric power plants by 2021.

The government agrees in principle on watering down the shutdown plan drawn up a decade ago by a center-left predecessor. But Merkel's coalition is divided over exactly how much longer to keep them running.

Merkel's environment minister has advocated a limited extension of up to eight years. Others, backed by German energy companies, want a 15-year extension or longer.

Merkel — a physicist by training — hasn't specified where she stands. She has said that she views nuclear power as a "bridging technology" until renewable energy such as wind power can be further developed.

However, Friday's appeal said that renewable energy remains too costly for now.

Among the signatories were the chief executives of Germany's biggest bank, Deutsche Bank AG; national railway Deutsche Bahn AG; chemical maker BASF AG; pharmaceutical company Bayer AG; retailer Metro AG; and the head of the Federation of German Industries.

They also included Oliver Bierhoff, Germany's national football team manager — along with the heads of the four companies that operate German nuclear plants.

Those companies also have complained loudly about plans to raise euro2.3 million ($3 million) per year to help combat Germany's budget deficit by levying a new tax on nuclear fuel. They are trying to negotiate an alternative.

New taxes "must not prevent investments for the future," the appeal said.

Merkel's spokesman, Steffen Seibert, said the appeal is "part of a discussion — there's no objection to that."

The government's intention is "to find an energy mix that enables this industrial country to continue ... producing the prosperity that we have become used to," Seibert said.

The center-left opposition, which set in motion the nuclear shutdown in 2000, fiercely opposes reversing it.

"We are experiencing an unprecedented wave of propaganda by the four nuclear companies, which want to brutally push through their interests," Sigmar Gabriel, the leader of the opposition Social Democrats, was quoted as telling the daily Saarbruecker Zeitung.