The Nord Stream 1, the biggest single pipeline carrying Russian gas to Germany, starts annual maintenance today, with flows expected to stop for ten days.
Some European governments, markets and companies worry that the shutdown might be extended.
The Nord Stream 1 pipeline transports 55 billion cubic metres (bcm) a year of gas from Russia to Germany under the Baltic Sea.
Last month, Russia cut flows to 40% of the pipeline's total capacity, citing the delayed return of equipment being serviced in Canada.
Europe now fears Russia may extend the scheduled maintenance to restrict European gas supply further, throwing plans to fill storage for winter into disarray, while heightening a gas crisis that has prompted emergency measures from many governments and painfully high bills for consumers.
German economy minister Robert Habeck said the country should confront the possibility that Russia will suspend gas flows through Nord Stream 1 beyond the scheduled maintenance period.
"Based on the pattern we've seen, it would not be very surprising now if some small, technical detail is found and then they could say 'now we can't turn it on any more'," he said at an event at the end of June.
Kremlin spokesperson Dmitry Peskov dismissed claims that Russia was using oil and gas to exert political pressure, saying the maintenance shutdown was a regular, scheduled event, and that no one was "inventing" any repairs.
Since March, Russia has cut off gas supplies completely to several European countries that did not comply with its demand for payment in roubles.
"The last few months have shown one thing: Putin knows no taboos. A complete halt to gas supplies through the Nord Stream pipeline cannot therefore be ruled out," Timm Kehler, managing
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