UK GAS-Prompt prices steady on balanced system

* UK gas system near balanced, undersupplied by 1 mcm

* Greece referendum could impact currencies

LONDON, July 2 (Reuters) - British wholesale gas prices for prompt delivery were steady on Thursday, with the system almost balanced, and eyes on external influences including Greece's financial crisis and gas supply negotiations between Ukraine and Russia.

Gas for next-day delivery was trading up 0.4 percent at 42.90 pence per therm by 0843 GMT, while gas for immediate delivery edged down 0.7 percent to 42.95 pence per therm.

National Grid (LSE: NG.L - news) data showed the system to be 1 million cubic metres (mcm) short, with demand forecast at 198 mcm and supply at 197 mcm.

The weather forecast is for warmer temperatures than seasonal norms over the coming week after parts of Britain had their hottest ever July day on Wednesday.

Analysts said the outcome of Greece's referendum on Sunday on its bailout terms would clearly have implications for the euro. Strengthening sterling against the euro is bearish for UK gas prices.

Another external factor which could impact gas prices going forward is Ukraine's ongoing discussions with Russia.

Ukraine said it halted natural gas imports from Russia on Wednesday after EU-brokered talks collapsed without a deal on how much Kiev should pay for its supplies and an interim accord expired at midnight.

Russian gas flows to the European Union via Ukraine were unaffected.

"Contracts further out on the curve are also offered sideways, with little impetus as yet from foreign exchange or oil markets, though further developments in the Russia/Ukraine payment situation could drive movements in winter delivery contracts," said Marcel Boonaert, head of trading and portfolio at Wingas UK.

Gas for winter 2015 delivery were unchanged at 47.70 pence per therm.

Dutch July gas prices at the TTF hub were 0.1 percent lower at 20.65 euros per megawatt-hour.

Imports from the Netherlands are expected to remain under pressure after the Dutch government ordered a further tightening of gas production at Groningen, Europe's largest gas field.

Europe's benchmark carbon price was 0.7 percent lower at 7.45 euros per tonne on ICE Futures Europe. (Reporting by Sarah McFarlane; Editing by Keith Weir)