By David Stamp
BERLIN (Reuters) - Germany has suspended a coalition agreement to delay closing the nation's aging nuclear power stations, Chancellor Angela Merkel said on Monday after the Japanese crisis stiffened opposition to an unpopular deal.
Last year, the coalition agreed to prolong the life of the 17 nuclear plants -- some of which are well over 30 years old -- beyond their original planned closure dates. On Monday Merkel said this agreement would now be suspended for three months.
As Japanese engineers struggle to avoid a meltdown at the Fukushima nuclear complex, Merkel faces a backlash on her nuclear policy before elections in the southwestern state of Baden-Wuerttemberg later this month.
One of Germany's oldest nuclear reactors is in the state, where Merkel's conservative CDU party risks losing power in the polls two weeks from now, partly because of rising support for the opposition Greens.
"We will suspend the extension of the life of Germany's nuclear power stations, which was decided only recently. The moratorium will last for three months," Merkel told a news conference, saying safety tests would be applied "without taboos."
The government had decided to keep the nuclear plants -- operated by E.ON, RWE, EnBW and Vattenfall -- running for about 12 years beyond their original shutdown date, despite protests even before the earthquake and tsunami hit Japan on Friday.
Environment Minister Norbert Roettgen said the moratorium meant that the Neckarwestheim I plant in Baden-Wuerttemberg, which is operated by EnBW, should be taken offline and was unlikely to start up again.
However, an EnBW spokesman said the utility would keep Neckarwestheim I operating pending talks with the government.
Later, a source quoted Bavaria's environment minister as saying that the Isar 1 plant in the southern state should also go offline.
On Saturday, anti-nuclear protesters formed a 45-km (27 mile) human chain from the Baden-Wuerttemberg capital of Stuttgart to Neckarwestheim I. Between 50,000 and 60,000 demonstrators took part, according to police and organisers.
A coalition source said RWE's Biblis A also faced a shut down. Under the original closure schedule both reactors, which began operating in the mid-70s, had been due to close this year.
Merkel said she was not worried about Germany's electricity supply as the country was a net exporter of energy. On Monday protesters gathered outside her office, waving banners saying "Atomic power? No thank you!."
Germany had been due to go nuclear-free after the last plant reached the originally planned end of its life in 2021. But pressure, largely from the power industry, grew to keep the stations open.
Last year's agreement was supposed to end months of division on the issue between the CDU and its junior coalition partner, the Free Democrats.
No new nuclear power stations have opened in Germany for decades because of public hostility, especially after the 1986 disaster when the Chernobyl plant in Ukraine exploded, spewing radiation across much of Europe.
(Additional reporting by Thorsten Severin, Andreas Rinke and Gernot Heller)