* Gustav shuts U.S. Gulf of Mexico oilfields, refineries
* Gustav expected to hit Gulf coast as Category 3
* Iran says $100 a barrel lowest acceptable price
(Recasts, updates quotes, forecast for Gustav)
By Matthew Robinson
LONDON, Sept 1 (Reuters) - Oil fell on Monday as concerns that Hurricane Gustav would cause severe damage to the U.S. oil sector eased as the storm failed to pick up strength as it barrelled toward the Louisiana coast.
Gustav -- which forced the shutdown of nine refineries and most U.S. offshore Gulf of Mexico oil production -- was expected to make landfall before midday local time as a Category 3 hurricane and its outer bands were already hitting the coast early Monday. [
]The storm failed to draw as much power as once feared, however, and forecasters said it was unlikely to grow stronger now and should weaken as it moves ashore.
For a graph on the projected path of Gustav, please click on: https://customers.reuters.com/d/graphics/STRM_GUSTAVU2.gif
U.S. crude <CLc1> fell $1.16 to $114.30 a barrel by 1436 GMT after opening for electronic trading several hours earlier than usual. Trade in the United States will be shut due to the U.S. Labor Day holiday.
London Brent crude fell $1.27 to $112.78 a barrel.
"It looks like Gustav is not going to be a Category 4, it's going to hit as a Category 3, and that's taking away some of the risk premium," said Thomas Stenvoll, UBS oil strategist, adding the market was waiting to see if Gustav severely damages oil infrastructure as it passes onshore.
At least 12.5 percent of total U.S. refining capacity was shut down ahead of the storm and other plants cut rates. The Louisiana Offshore Oil Port, the only U.S. port capable of offloading the biggest oil tankers, halted all operations.
Gustav is the biggest threat to the region -- home to a quarter of U.S. oil output and 15 percent of natural gas output -- since Hurricanes Katrina and Rita wrecked more than 100 offshore oil platforms in 2005 and closed several large refineries for months.
Nearly 2 million people fled the Louisiana coast and more than 11 million residents in five U.S. states were threatened by the storm. [
]The NYMEX declared force majeure on all delivery obligations under its August and September natural gas futures after ports and the Henry Hub delivery point were shuttered.
OPEC, RUSSIA
Iran's oil minister said on Sunday $100 a barrel was the lowest acceptable price for crude. Iran, OPEC's second-largest producer, has said the oil market is oversupplied as prices have dropped from the record high over $147 a barrel struck in July.
OPEC meets in Vienna on Sept. 9 to discuss output policy but other member nations have not come out and publicly backed Iran. Venezuela and Ecuador said on Friday that they expect the oil exporters group to maintain current output levels.
Traders are also eyeing ongoing tensions between Russia and the West, after Kremlin leader Dmitry Medvedev said on Sunday that Russia does not want a confrontation with the West but will hit back if attacked. Britain on Monday called for the European Union to suspend talks on a new partnership agreement with Russia to protest Moscow's military intervention in Georgia.
Russia, the top natural gas exporter and the No. 2 oil exporter, supplies more than a quarter of Europe's gas needs. (Additional reporting by Fayen Wong in Perth; editing by James Jukwey)