The European Commission wants countries in the bloc to cut their gas use by 15% by the end of the year.
If Moscow shuts off the taps this summer, the target will become legally binding.
The keyNordstream 1 line from Russia to Germany is offline for maintenance and will be turned back on this Thursday.
There are fears that Moscow won't follow through.
Germany is Europe's largest importer of natural gas in 2020, followed by Italy.
Russia has cut supplies to a number of countries which have refused to pay for gas in roubles.
Ursula von der Leyen said a Europe-wide cut-off was likely.
Russia is making us feel bad. Russia uses energy as a weapon. Europe needs to be ready for a partial or complete cut-off of Russian gas.
EU member states will vote on the rationing plan on July 26th.