UK GAS-Prices flat in market nervous over Ukraine crisis

* Gas system undersupplied by 4.7 mcm

* Demand 16 pct below seasonal norm

* Ukraine crisis supports prices

LONDON, April 10 (Reuters) - British wholesale natural gas traded near unchanged levels on Thursday morning as the market remained concerned that escalating tension between Russia and Ukraine could disrupt Russian gas supplies to Europe.

Gas for next-day delivery fetched 51.60 pence per therm at 0801 GMT, down 0.10 pence on Wednesday's close. Prices for delivery within the day were up 0.10 pence at 51.50 pence.

"There is still quite a lot of gas around but there is a real nervousness that this could change. There's a battle in the market at the moment between those who think there is too much of a risk premium in the price and those who think it should be higher," a gas trader said.

Traders said that fundamentally Britain's gas market is well supplied, as a mild winter led to higher-than-usual storage, but fears that Russia could cut supplies to Europe via Ukraine have buoyed prices.

With supply flows at about 207.7 million cubic metres (mcm) per day on Thursday and demand expected to be about 212.4 mcm, the system was just 4.7 mcm undersupplied.

Thursday's demand was about 16 percent below the seasonal norm of 253.3 mcm, National Grid (LSE: NG.L - news) data showed.

Above-normal temperatures have led to lower gas demand over the past few weeks but meteorologists at Thomson Reuters Point Carbon said cooler weather is likely to return by the middle of next week.

Norwegian pipeline operator Gassco intends to shut its Vesterled pipeline for annual maintenance from April 22 to May 19, tightening supplies to Britain, with several further shutdowns planned in May.

However, supply will be boosted by arrivals of liquefied natural gas (LNG) from Qatar.

The Lijmiliya LNG tanker is expected to arrive at the UK's South Hook LNG terminal on April 13, with the Umm Slal LNG tanker due there on April 15.

Gas prices further out edged lower, with the summer 2015 contract down 0.25 pence at 56.40 pence a therm by 0801 GMT.

In Britain's power markets, prices for day-ahead baseload (24 hours) delivery rose 0.10 pound per megawatt-hour (MWh) to 42.60 pounds a MWh.

GAS UK natural gas prices National Grid instant flows National Grid gas demand North Sea gas and power maintenance

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(Reporting by Susanna Twidale; Editing by Dale Hudson)