BERLIN (AP) -- Eager to prove that abandoning nuclear power won't force Germany to fall back on dirtier energy sources, a senior official on Thursday renewed government backing for offshore wind farms to fill the gap.

Rainer Baake, the deputy environment minister, conceded that environmental concerns and questions of shipping safety still have to be addressed before the first such installation is built, probably in 2004.

"We're treading new ground here,'' Baake told a conference on the technology in Berlin.

Environment Minister Juergen Trittin said last week that up to three-fifths of today's nuclear power could be replaced by wind energy by 2030. But none of the offshore plants that would produce that energy have yet been built, and there also is no agreement on where to build them.

On Monday, Chancellor Gerhard Schroeder and leading energy companies formally signed an agreement to shut down Germany's 19 nuclear power plants, making it the largest industrial nation to willingly forgo the technology.

The pact limits nuclear plants, which provide nearly a third of Germany's electricity, to an average 32 years of operation. That would likely see the most modern plants close around 2021.

The opposition Christian Democrats argue that eliminating nuclear energy would force Germany to use dirtier power sources. That could make it more difficult to curb emissions as outlined by the landmark 1997 Kyoto agreement on greenhouse gases.

The Environment Ministry plans to build about 40 wind generators offshore in a small-scale pilot project before 2004. Sven Teske, a spokesman for the environmental group Greenpeace, criticized the government for not moving ahead faster.

Wind power last year accounted for 2 percent of Germany's electricity production, or 10 billion kilowatt hours. Baake and Trittin want to see that figure rise to 110 billion kilowatt hours over the next three decades.