Russian President Vladimir Putin said on Wednesday that it was not clear in what condition the Nord Stream 1 turbine will be returned in after repairs in Canada, adding to uncertainty about the pipeline, which is due back in operation after maintenance.
Putin said that there was also a risk that the serviced equipment could be switched off, which would stop gas flows through Nord Stream 1.
Kremlin-controlled energy giant Gazprom cut gas exports to Europe via the route to 40% capacity in June, blaming delays in the return of a turbine that Siemens Energy was servicing in Canada.
That turbine, which was caught up in sanctions, was reported this week to be on its way back to be refitted.
"Now they are saying that they will return these machines, at least one of them. But in which quality will they be returned, what are the technical parameters after this repair, which is planned?" Putin said at a televised event.
"Maybe... they will turn it off at some point, and that's it, and Nord Stream 1 will stop, because they came from there, from Canada," Putin added without elaborating.
Nord Stream 1 is the single largest direct Russian gas supply route to Europe, It is due to restart gas exports on Thursday after a 10-day annual maintenance.
Putin also suggested earlier on Wednesday there might be a further reduction in supplies via the pipeline that runs under the Baltic Sea to Germany, Europe's economic powerhouse which has relied heavily on Russian fuel.
(Reporting by Reuters, Editing by Louise Heavens, Elaine Hardcastle)