Oil handed back early gains to stand below $94 a barrel on Monday as investors took profits, but concerns over the dollar's weakness and uncertainties about OPEC's moves to boost output continued to provide support.
OPEC's heads of state summit in Riyadh ended on Sunday without signaling whether the producer group would agree to pump more oil at its December 5 policy meeting in Abu Dhabi.
But of greater interest to investors was the push by Iran and Venezuela -- both locked in diplomatic rows with Washington -- for action to offset the falling value of their dollar-denominated oil revenues.
U.S. light crude was 51 cents down at $93.34 by 10:32 a.m. EST. It rose more than $1 in earlier trade to $95.15.
London Brent crude fell 41 cents to $91.21, off highs of $92.81.
OPEC talk about prices being undervalued and its concerns with the falling dollar are all filtering into the market, said Mark Pervan of ANZ Bank in Melbourne.
There are pockets of bullish news out in the market and no bearish news at all.
While the weak dollar was omitted from the summit's final statement, traders say the growing concern over the U.S. currency's predicament could prompt OPEC to seek a higher price.
Goldman Sachs said it did not believe the tumbling dollar was the main driver behind oil's rally, but rather tight global oil supplies.
We believe the currency impact on crude oil prices has been minimal and maintain that cyclical and structural factors have been the primary drivers behind the recent crude oil price rise, it said in its weekly energy report.
Barclays Capital analysts added that prices were receiving strong support from underlying tightness, though sentiment appears to be suffering from a slight resurgence of demand pessimism.
Oil has slid from an all-time high of $98.62 a barrel struck on November 7, as traders fretted about weakening oil demand in the world's top consumer and U.S. crude stocks unexpectedly rose, although the looming winter has lent fresh support.
Iran's president Mahmoud Ahmadinejad said the market price of oil was still undervalued.
Speculators on the New York Mercantile Exchange crude oil market cut their net long positions last week, the Commodity Futures Trading Commission said.
Net speculative crude positions fell to 27,566 in the week to November 13 from 105,816 in the previous week, which analysts at Barclays Capital said was the largest fall on record.
(Reporting by Randy Fabi and Santosh Menon in London and Fayen Wong in Sydney; editing by Anthony Barker)