New York's West Texas Intermediate (WTI) for delivery in June gained 24 cents at USD 100.84 a barrel. In London, Brent North Sea crude for June lost $1.46 to close at USD 108.12 a barrel.
The London benchmark felt selling pressure after Libya's state oil company declared the end of a force majeure on its Zueitina oil depot, opening the way for a resumption of exports from the terminal.
Analysts meanwhile said the sanctions by Washington and Western Europe, targeting Russian President Vladimir Putin's close business circle for Moscow's failure to stop soaring tensions in Ukraine, came in lighter than expected.
"The sharp turnaround in Brent oil prices is probably due to the fact the sanctions against Russia were not as tough as had been priced in," said Forex.com analyst Fawad Razaqzada.
"The Brent contract is likely to remain supported by geopolitical tensions for the foreseeable future, while the excess oil supply in the US will probably weigh down WTI."
Crude futures had rebounded in earlier trade, boosted by renewed strains between Russia and Ukraine. Ukraine, a major conduit for Russian natural gas exports to Western Europe, is monitored closely by investors who are concerned that a full-scale armed conflict will disrupt supplies and send energy prices soaring.
Washington placed seven Russian officials and 17 companies on its sanctions list, and the European Union added 15 people to its own blacklist, in hopes of persuading Moscow to back off from Ukraine. The measures fall short of the full-scale economic sanctions previously pressed by Washington.
"As the situation in Ukraine continues to remain tentative, we expect volatile trading conditions in the short term, until there is a clear resolution to the Ukrainian crisis," said analyst Myrto Sokou at the Sucden brokerage in London.