The UN cultural body, UNESCO, warned Wednesday it could remove Dresden's Elbe Valley in eastern Germany from the prestigious list of World Heritage sites, which would be a first in the 34-year history of the list.

"The World Heritage Committee decided that plans to build a bridge across the Elbe would have such a serious impact on the integrity of the property's landscape that it may no longer deserve to be on the World Heritage List," the World Heritage Committee, which is meeting in the Lithuanian capital Vilnius, said in a statement.

"It therefore decided to inscribe Dresden valley on the List of World Heritage in Danger with a view to also consider, in a prudent manner, delisting the site from the World Heritage List in 2007 if the plans are carried through," it added.

The Elbe Valley, which stretches 18 kilometers (11 miles), was added to the World Heritage List in 2004.

Elbe Valley joins 30 other threatened sites

In its statement, UNESCO described the Elbe Valley as "an outstanding cultural landscape that integrates the celebrated baroque setting and suburban garden city into an artistic whole within the river valley."

No site has ever been removed from the World Heritage List, which was established in 1972 and now numbers 812 natural and man-made sites around the world from the Giza pyramids in Egypt to the Great Wall of China.

With the addition of the Elbe Valley, the List of World Heritage in Danger now includes 31 properties. Earlier this week, the World Heritage Committee decided to remove four sites from the list: Cologne cathedral in Germany, Hampi in India, Djoudj National Bird Sanctuary in Senegal and Ichkeul National Park in Tunisia.

Dresden mayor calls decision "harsh"

In a referendum in February 2005, Dresden voters overwhelmingly approved the construction of the bridge over the Elbe River. The poll was legally binding and the UNESCO decision by no means would override the vote said Dresden mayor Lutz Vogel.

Vogel said Dresden regretted the placing of the Elbe Valley on the danger list, calling it a "harsh decision."

Vogel has now called for an extraordinary session of the city council on July 20 to discuss the matter. The bridge's construction could be put up for another vote if two-thirds of the council members support doing so. Further delays entail rising costs. Already, 10 to 15 percent of the 160-million-euro ($203 million) project has been spent in planning and preparation, Vogel said.