Russia announced Friday the completion of the controversial Nord Stream 2 gas pipeline to Germany, a project that has raised US concerns, divided Europe and angered EU ally Ukraine.
Nord Stream 2 is expected to double natural gas supplies from Russia to Germany, but it has raised tensions between the European Union and Washington.
Critics say the pipeline will increase Europe's dependence on Russian gas and bypass Ukraine.
The head of the Gazprom energy giant, Alexei Miller, announced Friday that construction was "fully completed."
A key controversy is that the pipeline diverts supplies from an existing route through Ukraine and is expected to deprive the EU's partner of crucial transit fees from Russia.
Ukraine -- in conflict with Russia since Moscow's 2014 annexation of Crimea -- has warned Europe that the pipeline could be used by Moscow as "a dangerous geopolitical weapon".
"Ukraine will fight this political project, before and after its completion and even after the gas is turned on," Sergiy Nykyforov, the spokesman of Ukraine's President Volodymyr Zelensky, told AFP.
A US State Department spokeswoman, Jalina Porter, said Washington would "continue to oppose this pipeline as a Russian geopolitical project that's a bad deal for Europe."
But Russian foreign ministry spokeswoman Maria Zakharova said critics should end efforts to block the project and instead agree "mutually beneficial terms" for its operation.
"It is clear to everyone, including critics of Nord Stream 2 and those who desperately opposed its construction, that it cannot be stopped," she said.
Kremlin spokesman Dmitry Peskov called for the project to be launched "as soon as possible" and said that "everyone" would benefit from it.
German government spokesman Steffen Seibert said that Nord Stream 2 had submitted a relevant application to the Federal Network Agency in order to begin operations.
Running from Russia's Baltic coast to northeastern Germany, the underwater, 1,200-kilometre (745-mile) pipeline follows the same route as Nord Stream 1, which was completed over a decade ago.
Like its predecessor, Nord Stream 2 will be able to pipe 55 billion cubic metres of gas per year to Europe, increasing the continent's access to relatively cheap natural gas at a time of falling domestic production.
- 'Victory for Russia' -
"It's a victory for Russia, especially taking into account the huge opposition the project has faced, from the US but also from European countries," Dmitry Marinchenko, a Fitch analyst, told AFP.
Besides Ukraine, countries such as Slovakia, the Czech Republic and Poland risk losing transit fees because of the pipeline, he added.
Gazprom has a majority stake in the 10-billion-euro ($12-billion) project. Germany's Uniper and Wintershall, France's Engie, the Anglo-Dutch firm Shell and Austria's OMV are also involved.
Former German chancellor Gerhard Schroeder serves as chairman of the Nord Stream's shareholders committee.
Russia and Germany insist Nord Stream 2 is a commercial project, but analysts disagree about its economic benefits.
A 2018 report by German think-tank DIW said it was unnecessary and undertaken based on forecasts that "significantly overestimate" demand in Germany and Europe.
Germany, Europe's top economy, imports around 40 percent of its gas from Russia, and Berlin believes the pipeline has a role to play in the country's transition away from coal and nuclear energy.
- US olive branch -
US sanctions on Russian vessels laying the pipeline succeeded in delaying Nord Stream 2, angering Germany.
But President Joe Biden, eager to rebuild transatlantic ties that were badly strained by his predecessor Donald Trump, waived sanctions in May on the Russian-controlled company behind the project.
Analysts saw the move as an olive branch to Berlin, whose support Washington is counting on in the face of other challenges, including a rising China.
Zelensky has said the sanctions waiver is a win for Russian President Vladimir Putin.
Reaffirming support for Ukraine, Biden hosted Zelensky at the White House in September.
After the meeting, Zelensky said Biden had assured him Washington would impose sanctions on the pipeline if there were "violations" from Russia that would create problems for Ukraine's energy security.
Critics of Washington's opposition to the pipeline point out that the US also wants to boost sales of liquefied natural gas (LNG) to Europe.