Russian energy giant Gazprom began 10 days of maintenance on its Nord Stream 1 pipeline on Monday – with Germany and other European countries watching anxiously to see if the gas comes back on.
The annual work on the gas link was scheduled long in advance. But the fear is that – with relations between Russia and the West at their lowest in years because of the invasion of Ukraine – Gazprom might take the opportunity to simply shut off the valves.
"Putin is going to turn off the gas tap... but will he turn it back on one day?" German mass-market daily Bild asked on Sunday on its website.
After the Nord Stream stop on Monday morning, Italian energy company Eni and Austrian Group OMV both reported their supplies from Gazprom had also been reduced.
"There are a number of scenarios in which we could end up in an emergency," Klaus Mueller, the head of Germany's federal gas network regulator, told public broadcaster ZDF on Monday.
"We are confronted with an unprecedented situation — anything is possible," German vice-chancellor Robert Habeck told public radio over the weekend.
"It is possible that the gas will flow once more, even at a higher volume level than before."
But, he warned, "it is possible that nothing comes through, and we still have to prepare for the worst" as Europe scrambles to transition away from Russia for energy supplies.
Moscow had already wound down supplies by 60 percent in recent weeks, blaming the absence of a turbine even as Berlin denounced what it calls a "political" decision.
Those cuts had a knock-on effect on supplies to a number of EU states, while Poland and Bulgaria have also seen theirs stopped altogether.
One issue at least was resolved over the weekend, when Canada agreed to return to Germany the turbine, which had been undergoing maintenance, despite the objections of Ukraine.
German Chancellor Olaf Scholz, via his spokesman, on Sunday welcomed "the decision of our Canadian friends" to grant what Ottawa termed a time-limited and revocable permit for Siemens Canada to allow the machine's return.
Berlin has also speculated that for technical reasons it would be difficult for Gazprom to stop deliveries via Nord Stream entirely.
As Habeck put it, "it is not like a water tap" that can simply be turned on or off, with gas extracted in Siberia not able to be stored indefinitely.
Following Russia's invasion of Ukraine in February, Germany suspended certification of a second pipeline, Nord Stream 2, as fears grew over Europe's massive dependence on Russian gas supplies.
But even now, a long-term shutdown of the pipeline would hit Germany and its EU neighbours hard, deepening an energy crisis in which uncertain supplies have pushed prices up ahead of Europe's winter.
Germany imports some 35 percent of its gas from Russia compared with 55 percent before the Ukraine conflict started.
In France, Economy Minister Bruno Le Maire said Sunday the country should ready itself for a "complete cut" in supplies from Russia.
"That is currently the most likely outcome," he said.
German industry is very vulnerable to shortages, with authorities discussing the possibility of having to ration supplies.
Chemical trade group VCI president Christian Kullmann told the Sueddeutsche Zeitung daily on Monday an end to supplies would amount to a "heart attack for the economy".
If deliveries cease altogether, German multinational chemical firm BASF is considering furloughing part of its roughly 1,00,000 workforce.
"We need to do everything to start saving gas now. Optimising heating, discussing it among families, preparing industry. We are not powerless," gas network regulator boss Mueller said Monday.
On Thursday, the German parliament adopted a plan which includes limiting winter heating on its premises to a maximum 20 Celsius and cutting hot water supplies in individual offices.