Russian pipeline operators say maintenance work is needed, but Germany suspects political motives.
Russian gas supplies to Germany via the Baltic Sea pipeline Nord Stream 1 have been halted for 10 days.
The pipeline’s Russian-backed operators say the move is because of annual maintenance work.
But German ministers believe the shutdown is politically motivated to put pressure on Berlin.
Last month, German Economy Minister Robert Habeck said Russian President Vladimir Putin was using gas “as a weapon” in response to EU sanctions.
In mid-June Russia’s state gas firm Gazprom cut gas flows through Nord Stream 1 to just 40% of the pipeline’s capacity. It blamed a delay in the return of equipment being serviced by Germany’s Siemens Energy.
The Canadian government says it will now return a repaired Siemens turbine to Germany for the pipeline. That move angered the Ukrainian government, which accused Canada of adjusting the sanctions imposed on Moscow “to the whims of Russia”.
Canada says it is granting Siemens Canada a “time-limited and revocable permit” to send repaired turbines back to Germany, despite the sanctions.
Germany’s government is worried that gas supplies could be reduced or cut permanently.
The pipeline shutdown is also affecting Italy, where energy group Eni said it would receive about a third less gas from Russia’s Gazprom on Monday compared with average volumes supplied over the past few days.
The head of the International Energy Agency, Fatih Birol, has warned that Russia may cut off gas supplies to Europe entirely and that Europe needs to prepare now.
Russia has already cut gas supplies to Poland, Bulgaria, the Netherlands, Denmark and Finland over their refusal to comply with a new payment scheme.
Since Russia’s invasion of Ukraine in February, Germany has reduced its dependence on Russian gas from 55% to 35% and wants to stop using gas from Russia altogether.
But if Russian supplies were suddenly cut overnight, this could tip Germany into a major recession, because entire industries rely on gas and most German homes use it for heating.
Germany’s gas storage facilities are currently about 64% full, German broadcaster ZDF reports.
Industry experts quoted by German media say the chemicals sector would be hardest hit by a gas shortage. It accounts for 15% of Germany’s gas consumption, and disruption could lead to shortages of goods such as fertiliser, pharmaceuticals, detergent and cosmetics.
German households and key services such as hospitals will be prioritised for gas supplies under a government emergency plan.