Germany on Thursday criticised a vote by US lawmakers on a bill that would sanction contractors working on a Russian pipeline to Germany, saying Washington should mind its own business.
"European energy policy is decided in Europe, not in the US," Foreign Minister Heiko Maas said on Twitter.
"We reject external interference and sanctions with extra-territorial effect as a matter of principle," he said.
The 9.5 billion euro ($10.6 billion) Nord Stream 2 pipeline will run under the Baltic Sea and is set to double shipments of Russian natural gas to Germany.
The German-Russian Chamber of Commerce (AHK) said the pipeline was important for the energy security of Europe as a whole and called for retaliatory sanctions against the United States if the bill passes.
"Europe should respond to sanctions that damage Europe with counter-sanctions," Matthias Schepp, head of the AHK, said in a statement.
Schepp said the sanctions would end up affecting European companies more than Russia.
Half of the project is financed by Russian gas giant Gazprom, with the rest covered by its European partners: Germany's Wintershall and Uniper, Anglo-Dutch Shell, France's Engie and Austria's OMV.
Despite its own diplomatic tensions with Russia, including over the murder of a former Chechen rebel in Berlin earlier this year, Germany has repeatedly defended the long-running project.
The economy ministry said it was awaiting the result of a Senate vote expected next week on the bill -- part of much wider US defence legislation.
US President Donald Trump has already said he would sign off on the measures if they are approved.
- Sanctions on assets, visas -
The bill requires the US State Department to report back within 60 days with the names of companies and individuals involved in pipe-laying for Nord Stream 2 and TurkStream, another pipeline from Russia to Turkey.
The sanctions envisioned by the bill include asset freezes and revocation of US visas for the contractors.
One major contractor that could be hit by the sanctions is Swiss-based Allseas, which owns the largest pipeline-laying ship in the world, the Pioneering Spirit, and has been hired by Gazprom to build the offshore section.
Europe is Russia's primary customer for natural gas and supporters of the 1,230-kilometre (760-mile) pipeline say it will provide reliable supplies at an acceptable price.
But it has been denounced by the United States and countries in eastern and central Europe, particularly Ukraine, which is currently a major transit country for Russian gas to Europe.
They fear the pipeline, which has an annual capacity of 55 billion cubic metres, will increase Europe's reliance on Russian energy supplies which Moscow could then use to exert political pressure.
Russia had hoped to unveil the pipeline in late 2019 but the launch has been delayed by difficulties in obtaining the permits from Denmark.
In October, Copenhagen gave Russia a permit to build a section of the pipeline on the Danish continental shelf in the Baltic Sea.
Russian Deputy Prime Minister Dmitry Kozak told reporters last month that he expected the pipeline to become operational in mid-2020.