EU law should govern Russia's new gas pipeline to Germany, France has said, heaping doubt on the project.
The Nord Stream 2 pipeline was meant to be monopolised by Russian energy firm Gazprom, according to original plans.
But the European Commission has tabled a law that would break up Russia's model by imposing EU rules on the offshore structure in the Baltic Sea.
"France intends to support the adoption of such a directive. Work is continuing with our partners, in particular with Germany, on possible changes to the [commission] text," French foreign ministry spokeswoman Agnes von der Muhll told press in Paris on Thursday (7 February).
She spoke ahead of a vote in the EU Council on the Nord Stream 2 bill on Friday.
Germany had counted on France, as well as Austria, Belgium, Cyprus, Greece, and the Netherlands to block it.
But the French U-turn would see Nord Stream 2 opponents, which include most eastern EU countries, Nordic states, and the UK, push it through.
"I would find it irritating if [French] president [Emmanuel] Macron made common cause with Polish nationalists a few days after the friendship meeting in Aachen," Markus Pieper, a German MEP in chancellor Angela Merkel's CDU party, said after the French announcement.
His reference to "Polish nationalists" came amid an EU clash with Poland's right-wing government on rule of law.
Macron and Merkel recently met in the German town of Aachen to sign a friendship treaty.
Merkel herself spoke more softly on Thursday.
"Do we become dependent on Russia due to this second gas pipeline? I say 'No', if we diversify at the same time," she said while on a visit to Slovakia.
Nord Stream 2 is already being built, with pipe-laying in the Gulf of Finland.
But if the EU commission law gets through, Gazprom will have to sell Nord Stream 2 gas via an independent intermediary.
It will also have to let competitors use the pipe, placing a legal bar on potential Russian cut-offs to EU clients.
The new legal regime would add to uncertainty around the project, amid US threats of sanctions on EU firms that promised to co-fund it
Russia itself walked away from a previous pipeline to Bulgaria, called South Stream, four years ago after the EU imposed similar legal conditions.
France did not publicly justify its decision on Thursday.
But a French government source had earlier told German daily Sueddeutsche Zeitung that Paris might do it due to "strategic problems" with Russia.
"We do not want to increase dependence on Russia and thereby harm the interests of EU countries such as Poland and Slovakia," the French source said.
Nord Stream 2 opponents fear it will help Russia to "blackmail" eastern EU countries such as Poland with gas cut-offs.
They also say it will remove barriers to further Russian aggression in eastern Ukraine by making Ukraine's EU gas transit pipelines obsolete.
"Nord Stream 2 would further increase Europe's vulnerability to Russian blackmail in the energy sector," the US ambassadors to Denmark, Germany, and to the EU wrote in an op-ed published by German broadcaster Deutsche Welle on Thursday.
"Cancelling the project would send a clear signal that Moscow cannot get away unscathed with its aggression against neighbouring states [Ukraine], and its meddling in our democracies," they added, referring to accusations that Russia had attacked US and French and German elections in recent years.
A bipartisan group of US senators tabled a resolution in Washington the same day "calling on European governments to cancel the Nord Stream 2 pipeline".
The EU commission and Berlin had in the past jointly urged the US to stay out of Europe's energy policy, despite the commission's own concerns on Nord Stream 2.
But US thinking on the pipeline is shared by senior figures in Merkel's party despite the power of the Russo-German business lobby in Berlin.
"That France places the good of European unity over solidarity with Germany is correct," Norbert Roettgen, the head of the foreign affairs committee in the German parliament, said on Thursday.
"It's not the fault of the French that we've isolated ourselves with Nord Stream 2 at the expense of the security concerns of other Europeans," the MP, from Merkel's CDU party, said.
Read the original text at EUobserver.