Oil prices rose today ahead of US inventory data expected to show spring refinery maintenance has begun to erode healthy fuel stockpiles.
Anxiety over oil producer Iran's nuclear row with the West and the shut-in of around a fifth of Nigeria's output also kept prices well above $60.
US light crude for April delivery was 50 cents higher at $61.85 a barrel, while Brent was up 60 cents at $62.36 by this morning.
"Rising US (crude) stocks could put a bit of pressure on prices, but I suspect we are at the time when stocks will stop rising and will start falling soon," said David Thurtell, commodities strategist at the Commonwealth Bank of Australia.
US crude stocks probably rose by 1.2 million barrels in the week ended February 24th, maintaining a robust surplus versus a year ago.
But gasoline inventories were seen steady and distillate stocks, including heating oil, falling by 1.3 million barrels as refiners shut down for spring maintenance, which could drain stocks in coming weeks.
Even if stocks remain ample for now, traders are nervous about supply disruption in key producing countries.
Chevron today said it had shut in 13,000 barrels per day of oil production in Nigeria because of a pipeline leak. There was no evidence the outage was the result of sabotage, but it added to unease following militant violence that has forced Shell to cut its Nigerian production by 455,000 bpd.
Apart from the actual disruption of Nigerian crude, traders were also nervous Iranian supplies could be affected by the dispute between the West and Iran. Iranian officials were meeting a Russian delegation on Wednesday for further discussion of Moscow's proposal to carry out uranium enrichment for the Islamic Republic on Russian soil.