A three-day halt of the Nord Stream pipeline -- a key source of natural gas for the European Union -- starts on Wednesday, and concerns are widespread that Moscow will find another excuse to clamp down on supplies, putting the region at the mercy of the weather.

Brent dropped 56 cents, or 0.5%, to $104.53 a barrel, WTI was at $96.86 a barrel, down 14 cents,

West Texas Intermediate was steady near $97 a barrel after jumping 4.2% in the week’s opening session amid concerns about the potential for supply interruptions in Libya

European natural gas prices on Monday plunged the most since March after Germany said its gas stores are filling up faster than planned.

Europe’s benchmark electricity price has risen to 10 times its decade-long average, in line with a 14-fold increase in the cost of gas, amid fears of shortages this winter.

With Russia squeezing gas deliveries and power-plant outages further sapping supply, pressure is growing on EU leaders to act quickly or risk social unrest and political upheaval.

Bern has been working to build up Switzerland's energy production and storage systems, but even the grand opening next month of a new, powerful pumped-storage hydroelectric plant is unlikely to help avoid problems this winter.

Brent rose 65 cents, or 0.6%, to $101.64 a barrel, WTI was up $1.22, or 1.3%, at $94.28

Benchmark Dutch front-month futures fell as much as 16%, partly reversing last week’s jump of almost 40%.

Brent climbed 73 cents, or 0.73%, to $100.07 a barrel, WTI rose 78 cents, or 0.84%, to $92.93.