UK GAS-Prompt prices slip on LNG supply

* Demand up almost 14 pct on seasonal norm

* Reduced flows from Norway due to Troll outage

LONDON, April 30 (Reuters) - British prompt natural gas prices were slightly lower early on Thursday as expectation of cargos of liquefied natural gas (LNG) outweighed an undersupplied system.

Prices for within-day delivery were at 45.15 pence per therm at 0845 GMT, down 0.05 pence from their last settlement.

Prices for delivery on Friday were down 0.35 pence at 44.95 pence per therm.

With supply flows at about 198.2 million cubic metres (mcm) per day on Thursday and demand expected to be about 226.5 mcm, the system was 28.3 mcm undersupplied, National Grid (LSE: NG.L - news) data showed.

Demand was almost 14 percent above the seasonal norm of 199 mcm, the data showed.

Traders said despite the system starting the day undersupplied there was confidence in the market that supply would be able to meet demand.

"Stock levels at the LNG terminals are pretty high and there are a few more ships on the way so the market is taking confidence from that," one gas trader said.

The Gharrafa LNG tanker is currently docked at Britain's Isle of Grain terminal while the Shagra tanker is expected to arrive in Britain on May 6.

Traders said supply from Norway could increase during the day if an outage at Norway's largest gas field Troll comes to an end. The outage, which started on April 27, was extended into Thursday and was expected to cut production by around 24 mcm per day, operator Gassco said.

Further along the curve, gas for May delivery was up 0.18 pence at 44.03 pence per therm.

In the Netherlands, the day-ahead gas price at the TTF hub was down 0.25 euros at 21.05 euros per megawatt-hour (MWh).

The benchmark European Union carbon price edged 0.1 euros higher to 7.60 euros a tonne on ICE Futures Europe.

(Reporting by Ahmed Aboulenein and Susanna Twidale; editing by Jason Neely)