At a regional summit of Baltic Sea nations, Putin expressed surprise at the "emotional response" to the Nord Stream pipeline, which would carry 55 billion cubic meters (1.9 trillion cubic feet) of natural gas annually between Russia and Germany.

"It's serious. We are worried about the dioxins and other poisons on the seabed," Estonian Prime Minister Andrus Ansip told reporters earlier Wednesday. "We expect our scientists to get full information about it all."

But Putin said the German-Russian joint venture had spent more than €100 million ($135 million) on researching environmental impacts, making it the largest such study in the region. Nord Stream said in December it had received approvals to construct the pipeline from Denmark, Sweden, Russia and Germany but was still awaiting a Finnish permit.

 

The Baltic Sea has been subjected to decades of nutrient deposits, toxic dumping, oil spills, weapons and untreated sewage. Experts say it's particularly vulnerable to environmental changes because it has only a narrow outlet to the Atlantic Ocean.

Putin pledged to reduce sewage deposits, saying his country would build water treatment plants in the Baltic Sea port of Kaliningrad. Sweden's Environment Minister Andreas Carlgren pledged to double his country's contribution to the Baltic Sea Action Plan to €9 million ($12 million).

 

The project produced strong reactions in Sweden and Finland. Pertti Joenniemi , an expert at the Danish Institute for International Studies, and EU4SEAS collaborator said it was "clear that the Baltic Sea region cannot become ... a model for European development unless the (environment and security) fears related to pipeline project are cleared out of the way."