UK GAS-Prices dip on robust LNG supply

* Within-day down 0.45 pence at 39.70 pence/therm

* System oversupplied by 6.9 mcm

LONDON, Aug 19 (Reuters) - Prompt natural gas prices in Britain opened lower on Wednesday morning as strong deliveries of liquefied natural gas (LNG) created an oversupplied market.

Prices for within-day delivery were trading at 39.7 pence per therm at 0655 GMT, down 0.45 pence since their last settlement.

Gas for September delivery was down 0.18 pence at 39.25 pence/therm.

Britain's gas system was oversupplied by 6.9 million cubic metres (mcm). Demand was forecast at 183.3 mcm while flows were expected to be 190.2 mcm/day, according to National Grid (LSE: NG.L - news) data.

Flows from the South Hook LNG terminal were about 60 mcm and volumes are expected to remain strong on Thursday because of the arrival of two tankers.

Supplies from the UK Continental Shelf are expected to pick up as gas flows resume from ConocoPhillips (NYSE: COP - news) ' Britannia platform after the end of maintenance work.

Prices were also lower on the Dutch TTF gas market, where day-ahead TTF gas was down 0.10 euros at 19.50 euros per megawatt hour.

In Europe's carbon market, benchmark EU Allowances (EUA) inched 0.02 euros lower to 8.26 euros a tonne. (Reporting by Nina Chestney; Editing by David Goodman)