British gas prices for delivery this week fell on Monday as warm weather forecasts weighed on demand, while curve gas rose with oil after Iran halted exports to British and French companies months ahead of a European Union embargo.

Gas for Tuesday delivery fell 0.15 pence to 57.85 pence per therm in Monday trading as the onset of exceptionally mild weather looked set to dampen demand and counter the closure of the UK's biggest underground storage site, Rough, on Wednesday and Thursday.

Centrica's decision last week to shutdown the site coincides with peak temperatures this week, making withdrawals from storage less necessary as warm weather erodes heating demand, traders said.

The Rough outage corresponds with peak temperatures so it shouldn't have any effect, a trader with a major European utility said.

Gas for delivery this week fell 1.20 pence, driven down by forecasts of rapidly rising temperatures, which are predicted to reach highs of 16 degrees Celsius on Thursday.

Gas for immediate delivery fell 0.15 pence at 57.85 pence as supplies ramped up over the course of the morning to meet demand. The UK gas network remained undersupplied at 1045 GMT but the gap between supply and demand was narrowing.

Further forward, the benchmark 2012 summer gas contract traded 0.20 pence higher at 56.45 pence as oil prices breached $120 a barrel following Iran's decision to pre-empt a European Union embargo on its oil exports by halting deliveries to British and French companies.

Fears of supply disruption from OPEC's second-biggest producer and upbeat economic data from the United States have kept oil prices high in the past month.

Seaborne gas shipments to the UK have seen sharp cuts in the past few months as the world's biggest producer Qatar diverts more supply to high-paying Asian markets, silencing Europe's spot market as deliveries are reduced to only contracted levels.

Analysts say that mass diversions to Asia could drive up spot prices at continental gas hubs over the long-term.

Furthermore, recent contracts for LNG by Asian buyers in Japan, Malaysia, Taiwan and Korea will divert increasing amounts of Qatari gas from the Atlantic to the Pacific market in coming years, according to Deutsche Bank.

The net result may be that gas prices in Europe will rise from the current $8/MMBtu to the $11-12/MMBtu contract price implied by current crude oil prices, putting UK gas prices on a more competitive footing with Asia.

WEATHER

The UK's Met Office forecast dry, bright and exceptionally mild temperatures in the south of England over the next five days, with mild spells continuing through the first half of March.

Although the UK is expected to see a warmer-than-usual March, temperatures are forecast to be colder than normal in April and May, while for the rest of Europe the outlook is mixed, according to Weather Services International.

DEMAND AND SUPPLY

Britain's gas network was 11 million cubic meters/day undersupplied even though demand was in line with seasonal norms of 329 mcm/day.

Shell on Monday announced maintenance work in April, August and September on two UK natural-gas terminals and one sub-sea pipeline in the North Sea, leading to reductions in supply to the UK gas market.

The announcement had no material impact on gas prices.

(Reporting by Oleg Vukmanovic; Editing by Alison Birrane)