(Changes to Thursday from Wednesday in paragraph 13)
* Obama: "isolation will deepen" if Moscow continues course
* US crude stocks rise 6.6 mln bbl, at Cushing drop 1.3 mln
* Iran May exports above agreed level
By Simon Falush
LONDON, March 27 Brent crude oil held steady around $107 a barrel on Thursday, underpinned by worries about potential supply disruption due to the possibility of Western sanctions on Russia's energy sector.
The United States and the European Union agreed on Wednesday to work together on preparing possible further economic sanctions in response to Russia's actions in Ukraine and to make Europe less dependent on Russian gas.
U.S. President Barack Obama warned at a news conference that "the isolation will deepen, sanctions will increase" for Russia, the world's biggest oil producer, if Moscow continues its current course.
Brent for May delivery was down 8 cents at $106.95 a barrel at 0934 GMT, after settling 4 cents higher.
"Given the geopolitical tensions, prices are well supported in the $105-$107 range," said Richard Mallinson, geopolitical analyst at Energy Aspects.
"If we do fall below $105 because of a weaker demand outlook, China is likely to start filling up some of the 80 million barrels of strategic and commercial storage capacity that it has built up."
U.S. crude for May delivery was down 13 cents at $100.13 a barrel, following a $1.07 rise in the previous session.
The contract was supported by a 1.33 million barrel fall in oil stocks at the Cushing, Oklahoma storage hub, the delivery point for U.S. crude futures.
The January start-up of TransCanada's 700,000 barrel per day (bpd) Gulf Coast pipeline accounted for the drop at Cushing. But a surge in crude stocks in the U.S. Gulf Coast to a record high suggested that the largest U.S. refinery hub was not able to use all the supply from Cushing.
Crude oil inventories nationwide rose by 6.6 million barrels, higher than analysts' expectations for a 2.7 million barrel build, with most of the rise on the Gulf Coast.
Refinery crude runs rose by 141,000 bpd as utilization rates edged up 0.4 percentage point, even while many refiners were undergoing maintenance.
"We had anticipated a far greater impact of seasonal refinery maintenance on crude stocks but still expect a deeper reduction in crude demand from refinery maintenance to emerge over the next month," Harry Tchilinguirian, head of commodity markets strategy at BNP Paribas, said in a note.
Following positive U.S. consumer confidence data on Tuesday, investors will look to final fourth-quarter GDP numbers and weekly jobless claims later on Thursday for further signs of economic growth in the world's biggest oil consumer.
Iran's oil exports have stayed above levels allowed under Western sanctions for a fifth month, according to sources who track tanker movements.
Supporting prices, supply was low from Libya and Nigeria. Oil theft is likely to push Nigeria off its spot as top African crude oil exporter in May, when exports could fall to their lowest since records began in 2009.
A preliminary loading programme, which excluded the Forcados and Ebok crude grades, showed Nigerian exports of around 1.59 million bpd in May, far below the 2011 highs above 2.2 million bpd.
Royal Dutch Shell declared force majeure on Nigeria's Forcados crude exports on Tuesday due to a pipeline leak caused by oil theft. (Additional reporting by Jacob Gronholt-Pedersen in Singapore; editing by Jane Baird)