Pressure mounted on German Chancellor Angela Merkel on Thursday to reconsider the Nord Stream 2 pipeline, which will take gas from Russia to Germany, after she said Kremlin critic Alexei Navalny had been poisoned with a Soviet-style nerve agent.
Merkel said on Wednesday that Navalny, who is being treated in a Berlin hospital, was the victim of a murder attempt using the nerve agent Novichok, and demanded an explanation by Russia.
Moscow has denied involvement and said the West should not leap to hasty conclusions.
Western countries have condemned the attack and many German politicians want a tough response.
"We must pursue hard politics, we must respond with the only language (Russian President Vladimir) Putin understands - that is gas sales," Norbert Roettgen, the conservative head of Germany's parliamentary foreign affairs committee, said on Thursday.
Late on Wednesday, he had said completion of Nord Stream 2 "would be the maximum confirmation and encouragement for Putin to continue this kind of politics".
Nord Stream 2 will double the capacity of the existing Nord Stream 1 pipeline from Russia to Germany.
Led by Russia's Gazprom with Western partners, the project is more than 90% completed and scheduled to operate from early 2021, which could make it hard to stop.
The project has split the European Union, with some members saying it will undermine the traditional gas transit state, Ukraine and increase the bloc's energy reliance on Russia.
The United States, keen to increase liquefied natural gas (LNG) sales to Europe, also opposes the pipeline and has targeted some companies involved with sanctions.
It is not clear Merkel, who has been unwavering in her support for the project, will bow to pressure.
Showing she was in no hurry to act, she said on Thursday any response depended on Russia's behaviour.
She said last week the Navalny case should not be linked to the pipeline, which is backed by Uniper, Wintershall DEA, Royal Dutch Shell, Engie and OMV.
Many in Merkel's pro-business conservative party want it to be finished.
A spokesman for Uniper, which has said it will lend up to 950 million euros to the project, said 2,300 km of the 2,460 km of the twin pipelines that make up Nord Stream 2 had been laid and Europe needed them.
"The pipeline and LNG infrastructure are both urgently needed to ensure secure, flexible and low-cost gas supply in Europe in the future," he said.
Former Social Democrat (SPD) Chancellor Gerhard Schroeder, a friend of Putin and lobbyist for Russian energy firms, has been involved with the pipeline.
Many in the SPD, which shares power with Merkel's conservatives, also back it but the head of the SPD parliamentary party said all options must be considered.
Prominent security analysts are also making the case for a tough stance.
"If we want to send a clear message to Moscow with our partners, then economic relations must be on the agenda and that means the Nord Stream 2 project must not be left out," Wolfgang Ischinger, chairman of the Munich Security Conference and a former ambassador to Washington, said.
(Additional reporting by Thomas Seythal and Vera Eckert, Editing by Gareth Jones, Timothy Heritage and Barbara Lewis)