STOCKHOLM — A plan by Russian-German consortium Nord Stream to build a gas pipeline under the Baltic Sea cleared two major hurdles Thursday as Sweden and Finland signed off on construction in their waters.

Nord Stream has raised fears both among environmental groups, who are worried about the impact on the Baltic Sea, and countries such as Poland, Ukraine and the Baltic states, which view the project as a threat to their energy security.

“Sweden gives permission for Nord Stream to lay two pipes on the continental shelf within the Swedish economic zone in the Baltic Sea for the transport of natural gas,” the government said in a statement.

The Finnish government said in a separate statement: “The project must be implemented so as not to prevent any potential subsequent energy, data communications or other infrastructure projects.”

It said the approval was valid for the next 50 years, after which it would have to be renewed.

Prime Minister Vladimir Putin, who has personally lobbied for the construction of Nord Stream in the last few years, thanked Sweden and Finland for their decisions at a government meeting in Moscow.

The pipeline, which will deliver 55 billion cubic meters of gas per year from Russia to Germany via the Baltic Sea, still needs final approval from Finnish environmental officials, with a decision due by the end of 2009.

Denmark gave its assent last month, leaving Russia and Germany as the last countries to sign off. A Nord Stream spokesman said decisions from those countries are expected by the end of 2009.

Sweden said Nord Stream had agreed on a number of conditions to ensure that the project met environmental requirements both during and after construction.

“There are now several terms and commitments from the company to safeguard the Baltic Sea’s environment, fishing and shipping,” Environment Minister Andreas Carlgren said.

“According to national authorities, the impact on the Baltic Sea’s environment is very limited and only prevalent for a short while in connection with the construction work.”