UK GAS-Prompt prices ease, under pressure from currency move

* System under supplied by 7 mcm/day

* Rough inventory at low level for this time of yr- analysts

LONDON, May 5 (Reuters) - British prompt gas prices eased on Tuesday after the pound strengthened against the euro, while later-dated contracts were supported by low stocks.

Gas for within-day delivery was down 0.3 percent at 44.00 pence per therm, while gas for day-ahead delivery was down 2.6 percent at 44.00 pence per therm by 1031 GMT.

National Grid (LSE: NG.L - news) data showed supply was forecast at 196 million cubic metres (mcm) on Tuesday, while demand was seen at 203 mcm, showing the system was under supplied by 7 mcm.

"The main driver this morning is the EUR/GBP retrace," a trader said.

Sterling firmed around 0.5 percent against the euro early on Tuesday.

Meteorologists forecast temperatures above normal levels from Friday, which is likely to weaken demand for gas for heating.

Gas inventory at Britain's largest gas storage facility Rough is at an all-time low of 487 mcm for the time of year, according to Thomson Reuters Point Carbon analysts.

In March, Centrica Storage Ltd (CSL (Other OTC: CMXHF - news) ) said it expected the limit on the maximum stock level held at Rough would last up to six months, while the site is to undergo "testing and verification works".

This means the facility can still fill in the third quarter ahead of winter, assuming the cap is lifted by then, traders said.

Gas for delivery in the third quarter was up 0.5 percent at 42.60 pence per therm.

In the Netherlands, the day-ahead gas price at the TTF hub was down 2.6 percent at 20.25 euros per megawatt-hour.

The benchmark European Union carbon price was trading 0.5 percent lower at 7.58 euros a tonne on ICE Futures Europe. (Reporting by Sarah McFarlane; Editing by Ruth Pitchford)