UK GAS-Prompt prices edge higher on undersupply

LONDON, July 17 (Reuters) - Prompt British gas prices edged higher on Monday morning, as strong exports to the continent left the British gas system slightly undersupplied. * Within-day gas price up by 0.20 pence to 33.60 pence/therm at 0840 GMT. * UK gas system undersupplied by 7.5 million cubic metres (mcm), with demand forecast at 207.8 mcm and flows at 200.3 mcm/day, National Grid (LSE: NG.L - news) data showed. * Traders said exports to the continent, via the InterconnectorUK (IUK) pipeline with Belgium, were high due to strong gas demand in Europe. * "Continental (IOB: 0LQ1.IL - news) gas demand is quite robust due to high gas-to- power demand," a gas trader said, adding that high coal prices had led to some fuel switching, from coal to gas. * Exports from Britain to the continent through the IUK pipeline near full capacity around 57 mcm. * The front-year European API2 2018 coal contract rose $0.92 to $71.75 a tonne. * August gas contract up by 0.28 pence to 34.00 p/therm. * Day-ahead gas price at the Dutch TTF hub down by 0.01 euro to 14.90 euros per megawatt hour. * Benchmark Dec-17 EU carbon contract flat up by 0.01 euro to 5.43 euros per tonne. * Thomson Reuters (Dusseldorf: TOC.DU - news) analyst view: http://emea1.apps.cp.extranet.thomsonreuters.biz/cms/?pageid=united-kingdom-gas (Reporting by Susanna Twidale; editing by Nina Chestney)